Paid Family Leave

The Family and Medical Leave Act (FMLA), enacted in 1993, is currently the primary federal policy to support parental and family leave in the United States. The FMLA mandates that qualifying workers receive 12 weeks of unpaid, job-protected leave with continuous health insurance coverage.⁴⁵ Firm size and work history requirements preclude some employees from taking time off through the FMLA, however. To qualify, employees must have worked at least 1,250 hours in the preceding year, must work in a firm with at least 50 employees, and must have worked for that employer for the past 12 months.² Data show that only 60 percent of workers qualify for the FMLA.³ Research has also found that the policy largely benefits higher-income and White workers.⁴ Because the FMLA provides only unpaid leave to eligible workers, many low-income parents may not use the time off or may shorten the duration of leave so that they do not lose wages. In December of 2019, a new law was passed that provides 12 weeks of paid parental leave to federal civilian employees who are otherwise covered by the FMLA, slated to go into effect on October 1, 2020.⁵

Given the limitations of the FMLA, several states have begun to adopt statewide paid family leave policies. Paid family leave policies allow parents time to bond with a new biological, adopted, or foster child. These policies often include medical leave provisions, allowing individuals to take time off for their own disabilities or to care for ill family members, but the focus of this summary is on parental leave only. Paid family leave policies currently allow parents to take between 4 and 12 weeks off from work, depending on the state, with pay varying based on a proportion of the employee’s wages prior to taking leave. Most state policies also have weekly payment caps and require that individuals have a minimum work history, by hours or earnings, in the state during a given “base period” (often 12 months) prior to leave-taking.

Who Is Affected by Paid Family Leave?

Paid family leave policies govern how much paid time off employers must provide to an employee after a birth, adoption, or placement of a foster child. According to the most recent available data from the Leave Module of the American Time Use Survey, 2017-2018, 50.5 percent of workers who are not self-employed reported that they had access to any paid family leave, regardless of state policy, whether through a formal family or medical leave benefit, or through other forms of paid time off, such as vacation days.ⁱ In contrast, a minority of Americans in 2019 (19 percent) reported access to a paid family leave benefit specifically designed for the purpose of caring for a child or family member,⁴¹ and 89 percent reported access to unpaid family leave.^ii,6

What Are the Funding Options for Paid Family Leave?

The majority of states that offer paid family leave fund it through employee payroll taxes; California, Connecticut, Massachusetts, New Jersey, New York, Rhode Island, and Washington all use this funding mechanism. The District of Columbia finances its program through employer contributions, and Oregon funds its program through both employee and employer contributions.

1. Calculations were done by the Prenatal-to-3 Policy Impact Center.
2. The sum of paid and unpaid leave exceeds 100 percent because some workers had access to both types of leave.

Paid family leave is designed to allow parents time off from work to bond with a new child. The guarantee of paid family leave may increase parents’ labor force participation and families’ economic security after a birth.⁷ Specifically, if parents are able to maintain employment and receive a portion of their salary when a new child enters the family, parents may be more likely to stay engaged in the workforce long-term, which is associated with indicators of greater economic security,⁸ such as higher income and a lower risk of poverty.⁹ In particular, continued attachment to the pre-birth employer could reduce time spent looking for work and allow parents to build job-specific skills over time. If parents with access to paid leave remain attached to the workforce to a greater degree than families without paid leave, then affordable and high-quality child care must be accessible to support children’s development when parents work.⁴⁴

Additionally, paid family leave may positively impact parent and child health outcomes.¹⁰ Paid family leave should help new parents have more time to bond with their babies, develop positive caregiving skills, and build the foundation for healthy attachment.¹¹ Mothers with access to paid family leave may be less likely to experience depression and more likely to engage in healthy behaviors, such as stress management and exercise.¹⁰ Children may be more likely to experience positive health outcomes if their families have access to paid family leave.¹² Mothers who are able to take paid time off after the birth of a child may be more likely to initiate breastfeeding and continue breastfeeding longer.¹² Furthermore, both mothers and children may have a lower likelihood of being hospitalized following childbirth, because families may have more time to seek prompt medical care if a need arises.¹³ Children may be less likely to experience longer-term poor health outcomes that are avoidable through timely and frequent preventive care initiated during infancy.¹²

The evidence for the impact of paid family leave in the United States reveals that the policy improves a variety of child and family outcomes, but the research only represents a few states. Only California, New Jersey, and Rhode Island had family leave laws that were in effect before 2018. The oldest family leave laws have been in effect in California and New Jersey since 2004 and 2009, respectively, and these laws have expanded and evolved since their initial implementation. Therefore, many states have not had family leave laws for enough time to study the impacts in a rigorous way. Although most countries outside of the United States have implemented paid family leave and many international studies have found positive impacts, the effects of those laws must be considered within the broader context of universal child care, universal health care, and child allowances in some countries.⁴³ Due to these systemic policy differences, examining laws within the US is the best basis for building evidence on the policy’s effectiveness for families in this country.

The research discussed here meets our standards of evidence for being methodologically strong and allowing for causal inference, unless otherwise noted. Each strong causal study reviewed has been assigned a letter, and a complete list of causal studies can be found at the end of this review, along with more details about our standards of evidence and review method. The findings from each strong causal study reviewed align with one of our eight policy goals from Table 1. The Evidence of Effectiveness table below displays the findings associated with paid family leave (beneficial, null,ⁱⁱⁱ or detrimental) for each of the strong studies (A through R) in the causal studies reference list, as well as our conclusions about the overall impact on each studied policy goal. The assessment of the overall impact for each studied policy goal weighs the timing of publication and relative strength of each study, as well as the size and direction of all measured indicators.

Table 2: Evidence of Effectiveness for Paid Family Leave by Policy Goal

*Effects of paid family leave on long-run employment were statistically significant in the negative direction for first-time mothers, but were null for all mothers considered.
**Effects of paid family leave on earnings were negative for first-time mothers, but null for all mothers considered.
⁺This study examined reading, but not outings and meals.

Access to Needed Services (Leave-Taking)

Research from California found that the implementation of paid family leave was associated with mothers and fathers taking longer leave and both parents taking leave simultaneously.^B,N,R A 2013 study found that the policy doubled maternal leave-taking (paid or unpaid) from an average of 3 to 6 weeks,^N and a 2016 study found that leave-taking increased by 5 weeks for mothers and 2 or 3 days for fathers.^B A 2018 study found that the policy increased the probability of fathers taking leave by 46 percent, but fathers were still taking only an average of 1.5 weeks out of the 6 weeks that were available at that time in California.^R  The study noted that mothers took an average of 9 weeks out of the 12 paid weeks available through both Temporary Disability Insurance and paid family leave at that time.^R

Research suggests that the effect on leave-taking may be greater for unmarried women and Black women than other groups; the 2013 study mentioned above found that Black mothers’ probability of taking any leave increased by 10.6 percentage points from a rate of 2 percent prior to California’s paid leave policy.^N White mothers, meanwhile, saw a 4 percentage point increase from a rate of 7 percent prior to the policy. However, more research on leave-taking effects by subgroup would be valuable to corroborate these findings, which had fairly large standard errors.

Although the policy has increased the uptake of maternity leave, one study found that only approximately 40 percent of eligible mothers in California took advantage of paid leave benefits 10 years after implementation.³¹ The study also found that “median earnings of leave takers are an estimated $10,000 higher than the median income for all working women in California” (p. 1).³¹ Although some of this difference may be attributed to differential likelihood of eligibility, research also suggests that awareness of eligibility is low: a 2011 study found that only half of eligible adults reported they knew about California paid family leave, with lower-wage earners least likely to know about it.⁷ Increasing awareness of the program could boost participation and allow more families, especially lower earners, to reap the child and parental benefits supported by the evidence, discussed below.

Parents’ Ability to Work

Overall, research on the impact of paid family leave on mothers’ employment and labor force participation finds mostly positive results. A 2016 study of California’s policy found that paid family leave increased the probability of mothers working 1 year after a birth by 12.9 to 18.3 percentage points, depending on how much work experience the mother had before the birth.^B The policy increased weeks worked and average weekly work hours during the child’s second year by 7.1 and 2.8, respectively, for those who worked at least 20 weeks during their pregnancy.^B Additional research has shown that paid family leave is associated with higher labor force participation among young women.^D,F,Q For example, one study of California and New Jersey’s policies found a 5 to 8 percentage point increase in the labor force participation rate of mothers in the months surrounding birth, as well as a significant increase in weeks spent with a job, compared to weeks spent looking for work.^D A second study that examined both states similarly found a positive impact on labor force attachment – in California, the authors found that paid leave reduced labor market exit by 20 percent through 5 years after a birth, and in New Jersey, the effects averaged 46 percent through 5 years.^Q The authors found that the effects were concentrated among women with higher educational attainment.

A 2013 study found that among mothers who worked following a birth, those who had access^iv to paid leave saw a 6 to 10 percent increase in weekly work hours, with an increase of 10 to 17 percent in work hours among those who reported having worked in the prior calendar year.^N The study found no significant effect on the likelihood of employment overall.

Another study found that labor force participation increased by 1.4 percentage points in California following the implementation of paid family leave.^F The study, however, also reported unanticipated effects of paid family leave: a significantly higher unemployment rate (an additional 1.5 percentage points) and a longer duration of unemployment, at 1.6 weeks longer.^F The author speculated that paid family leave may result in higher labor costs, and employers may be less inclined to hire younger women, causing higher unemployment rates in this group. However, this theory was not tested in the study, and other research suggests no such effect on employers.⁷

A 2019 study of California’s paid leave policy, one of the largest studies on paid leave to date, found negative impacts on employment and wages in the long run among first-time mothers who took leave immediately after the policy was implemented in 2004.^A The authors found a reduction of 7 percent in maternal employment and an 8 percent drop in wages 6 to 10 years after giving birth among women whose first birth was timed such that they were eligible for paid leave (compared to those who gave birth a few months before implementation). However, the authors found that self-employment income offset some of the decrease in wages. The rationale for focusing on first-time mothers was that “the availability of paid leave may…have a greater impact on new mothers than on women who have already established their child care and work routines [because] women learn how to manage motherhood when they have their first child”(p. 16).^A The long-run employment findings for all mothers eligible for paid leave were not statistically significant, but employment was 0.2 percentage points lower than expected in the long-run (5 to 11 years after the birth) among this group.

Findings for job continuity, or attachment to the pre-birth employer, are mixed but lean positive. A 2018 study examined the impact of benefit levels using a sample of mothers just above and just below the maximum weekly benefit in California (high-earning women), and the authors found that a 10 percent increase in the weekly benefit amount increased the likelihood that a mother would return to her pre-birth employer by up to 5 percent.^O A 2016 study with a broader sample found a positive and statistically significant 13 percent increase in the likelihood of working at the pre-birth job 1 year after the birth with a paid family leave policy.^B Very small and insignificant effects on job continuity were found in a large 2019 study, however.^A

Sufficient Household Resources

A study from California with a large sample found that paid family leave was associated with better economic security for families.^M The study found that household income was approximately $3,400 higher (4.1 percent) among families with access to paid family leave relative to those who did not have access, and the effects were greater among married mothers, likely because they tend to take longer leaves than single mothers. The study also showed that families with access to paid leave were 10.2 percent less likely to be in poverty, resulting in a 2 percentage point reduction in the poverty rate, with the greatest effects for less-educated, low-income, single mothers.^M

A 2013 study found that an increase in weekly work hours for mothers who took paid leave led to very small, and statistically insignificant increases in wage income.^N A 2016 study found an insignificant effect of paid leave on hourly wages 1 year after the birth, with impacts ranging from a 3.6 percent increase to a 5 percent increase depending on how many weeks the mother worked during pregnancy.^B Finally, a 2019 study found that paid family leave had a detrimental effect on the long-run annual wages of first-time mothers, with a net 10-year loss of $24,000.^A However, the authors noted that because they found increases in first-time mothers’ time spent with children, their results could also be interpreted as “an increase in investment of $24,000 worth of mothers’ time in children” (p. 26).^A,36

Parental Health and Emotional Wellbeing

Two studies of California’s policy found that parents’ physical and mental health benefited when parents had access to paid family leave. A 2019 study found that mothers with access to paid family leave were more likely to report having very good or excellent mental health (a 7 to 17 percentage point increase, depending on the control group examined^v) and coping well with the day-to-day demands of parenting (a 3 to 5 percentage point increase).^C Effects on paternal mental health were not significant in this study and trended in both positive and negative directions, depending on the age of the child at data collection and the control group examined. A 2020 study found multiple positive impacts on parent health (including mothers and fathers): a significant, 11 percentage point increase in the likelihood of reporting very good or excellent health, a 0.79 point reduction on a 24 point scale of psychological distress, an 8.2 percentage point decline in the risk of being overweight, and a 12 percentage point decline in any alcohol consumption.^P Mothers reported greater impacts on distress and overall health, whereas fathers saw greater declines in alcohol consumption.

Nurturing and Responsive Child-Parent Relationships

Two studies offer evidence that paid family leave increases the quality of parent-child relationships.^A,C A 2019 study, using data from the Survey of Income and Program Participation, found that California’s paid family leave policy led to mothers spending more time with their children up to 4 years after the birth; in particular, mothers who took paid leave reported reading to their children 11.4 more times per week, going on outings with children 9.8 more times per month, and having breakfast with their children 3.6 more times per week than those who did not take paid leave.^A The effects for all who had access to paid leave, rather than the smaller sample of those who took it, were smaller but still positive. A second study also examined reading, and found that parents were 10 to 20 percent more likely to read to their infants 4 or more days per week when they had access to paid leave in California, depending on the control group.^C

Optimal Child Health and Development

Evidence shows that parents with access to paid family leave in California saw improvements in a variety of measures of their infants’ health and later child health in elementary school. In particular, increases in breastfeeding have been cited in multiple studies.^G,H,K

Three studies present evidence that access to paid family leave increases breastfeeding,^G,H,K which has been linked in some research to a number of beneficial impacts for infants, including stronger immunity, reduced infections, and reduced infant mortality.³² A study with a very large sample from California and New Jersey showed that paid family leave policies increased the percentage of exclusively breastfed infants at age 6 months by 1.3 percentage points.^G The study also found statistically insignificant but positive effects on any breastfeeding at 6 and 12 months. The authors noted that the relatively small overall effects found may underestimate the true effects among working women, who are more likely to be affected by paid family leave, because the sample included both working and non-working women.

A second study found that in California, paid family leave led to a significant 5 percentage point increase in the likelihood of breastfeeding at 6 months, and a marginally significant^vi increase in breastfeeding duration of 18 days, from a base of 221 days on average.^K There was no significant overall effect found for breastfeeding initiation, however; the authors suggested that because many women had access to 6 weeks of paid leave through Temporary Disability Insurance, they were already quite likely to initiate breastfeeding prior to the new paid leave policy (85 percent of mothers breastfed). However, the policy had significant effects on breastfeeding initiation among some subgroups. For example, the study found the greatest effects for Black mothers (a 7.5 percentage point increase in the likelihood of breastfeeding at all) and for mothers with incomes below 50 percent of the federal poverty level, with a 5 percentage point increase in likelihood of breastfeeding.^K Overall, the study found greater effects on breastfeeding for less-advantaged groups, including those with lower education levels.

An additional study from California with a higher-income and less generalizable sample showed that paid family leave led to an increase of 3 to 5 percentage points in exclusive breastfeeding at 6 months, and an increase in breastfeeding at all for at least 3, 6, and 9 months that ranged from 10 to 20 percentage points.^H

Other outcomes may benefit from paid family leave policies as well. A study of California found that after the paid leave policy went into effect, hospitals saw 3 to 6 percent fewer infant admissions, particularly for avoidable conditions—hospital admissions decreased 25 to 33 percent for upper respiratory infections and 9 to 15 percent for gastrointestinal diseases.^L The authors suggested that increased breastfeeding, and parents having more time to seek preventive care for their infant, may have driven these results. However, the study did not examine breastfeeding and preventive care as outcomes. Another California study found that infants in families with access to paid family leave were 1.4 to 5 percentage points less likely to receive late vaccinations (measured for vaccines typically given before 6 months old), depending on the specific vaccination, and the effect was even stronger for families with low income, with a 5 to 7 percentage point reduction in the likelihood of receiving a late vaccination relative to similar families in states without paid leave.^E

A third study revealed that California’s policy boosted the likelihood that a child had very good or excellent health, as reported by their parents, by between 4.8 and 8.6 percentage points, depending on the control group examined.^C  The study also found a significant reduction in the likelihood of asthma (2.7 percentage points) for infants under age 1 year, and a reduction of 5 percentage points for all children ages 0 to 17. Results for food and respiratory allergies were mixed, with mostly null impacts except for a significant decline of 2.5 percentage points in respiratory allergies for infants under age 1.

Paid family leave also appears to be linked to better child health in elementary school, suggesting that the policy can have long-lasting beneficial impacts beyond the infant years. A 2017 study showed that children whose families had access to paid family leave were less likely to be overweight (4.1 percentage points), have ADHD (0.7 percentage points), have hearing problems (2.4 percentage points), and have communication problems (1.1 percentage points), with greater effects seen among boys and among children with lower socioeconomic status for the likelihood of being overweight and having ADHD.^J

Finally, a 2016 study showed that paid family leave was linked to a significant reduction in the rate of pediatric abusive head trauma in children below age 2.^I For children below age 2, paid family leave led to a rate reduction of 2.8 cases per 100,000 children; for children under age 1, the policy led to 5.1 fewer cases per 100,000 children.^I The authors suggested that this may be driven by reduced maternal stress and better mental health after the introduction of paid leave, a mechanism supported by other studies reviewed.^C,P

3. An impact is considered statistically significant if p<0.05.
4. For the purpose of their analyses, most studies included in this review defined “access” as “living in a state with a paid family leave policy” and examined outcomes relative to timeframes prior to implementation of the policy, relative to families in states without a paid leave policy, or relative to families without infants or young children. “Having access” does not mean that every family in the treatment sample was eligible for paid leave or received benefits.
5. The authors analyzed and reported differences for infants and children in neighboring states, in other large states, and in all states except California.
6. An impact is considered marginally significant when p<0.10.

Several studies examining economic and child outcomes have found strong effects on leave-taking, labor force participation, and child vaccinations for mothers with low educational attainment, Black mothers, and those with low socioeconomic status.^{B,D,E,J,K,M,N} One study showed greater improvements in maternal mental health and coping skills among low-income families,^C and another found that reductions in child incidence of overweight and ADHD were concentrated among less-educated and lower-income families.^J

One study showed that the effect of increased breastfeeding following the implementation of paid family leave was greatest among higher-income, older, White, and married mothers,^G compared to Black and Hispanic mothers and younger mothers with lower income. However, another study found that Black mothers saw a greater increase in the likelihood of breastfeeding initiation when they had access to paid family leave than did White and Hispanic mothers and those of other races.^K  Significant gaps in breastfeeding initiation and duration remain between racial and ethnic groups,³³ but research suggests that paid family leave may help narrow the gaps given the larger effect of the policy for Black mothers identified in some studies.

7. Disparities are defined here as differential outcomes by race, ethnicity, or socioeconomic status (SES).

Despite initial concern about the impact of the policy on employers and businesses, studies have found that most employers report “no noticeable effect” or “a positive effect” of paid family leave on employee productivity, profitability, turnover, and morale.^7,34 Some businesses have found that paid sick leave makes it more likely that employees will receive preventive health care, reducing later health care costs,³⁵ but more rigorous research on the return on investment for paid family leave, beyond employer surveys, is needed to build the evidence base. A more comprehensive analysis of the return on investment is forthcoming.

The research to date shows that the implementation of paid family leave policies in the United States is effective at supporting labor force attachment and improving maternal and child health and parenting outcomes. The evidence from the most methodologically rigorous studies shows that parents take longer periods of family leave and that families achieve greater economic security when they have access to paid leave. Additional research also shows positive effects for maternal health and for a variety of child health outcomes.

However, effects may differ for first-time mothers compared to mothers with other children at the time they take paid leave. A recent, large study found negative long-term effects on employment and wages among first-time mothers who took advantage of California’s paid leave policy immediately after implementation, with insignificant effects for all mothers in the sample.^A The authors suggested that because they only followed women who took leave when it first became available, the effects may not be generalizable to all women.³⁶

Although the current evidence generally supports positive impacts, most of the research to date comes from two states because of the recent enactment and implementation of statewide leave laws. More time is needed to fully assess the impact of paid family leave as additional states begin to implement their laws and other states continue to expand the generosity of their policies. Additionally, the current research is not able to assess the complete impact of paid family leave for lower-income families and fathers, whose take-up rates are lower.^31,N Few studies focus on how fathers are affected by paid family leave, despite the fact that research from other countries has shown positive outcomes for the entire family if fathers take paternity leave.³⁷ Noncustodial fathers are absent from the research. Reliable data on access to paid leave and leave-taking across the US are also limited; the Bureau of Labor Statistics’ American Time Use Survey does not provide sufficient sample sizes in every state to gain a comprehensive picture of access to, and take-up, of paid family leave.

The evidence to date shows mostly positive outcomes for less-advantaged populations, but at least one study showed greater effects on breastfeeding for more advantaged mothers.^G Further research is needed to understand how specific populations are affected by paid family leave, and how to decrease disparities between parents of different races, ethnicities, and socioeconomic statuses.

Finally, a more nuanced understanding of the optimal length of paid family leave, the percent of pay, and the best funding source is necessary to highlight the specific components of paid family leave that lead to the greatest impacts on health and wellbeing. Findings from three studies that were not included in this review because of limitations in the study design or a focus on factors other than statewide policy suggested that the benefits of paid leave may accrue when mothers take more than 6 weeks – in particular, maternal mental health and breastfeeding outcomes may be better when mothers return to work after 12 weeks of leave.^38,39,40 However, rigorous research on state policy in the US currently only extends to 6 weeks, as many states are just now implementing their paid leave policies and extending the available leave to beyond this level.

If a state aims to ensure that new parents have the time, services, and economic security they need to help their infants achieve and sustain a strong and healthy start in life, the evidence suggests that implementing a paid family leave policy of at least 6 weeks will help reach these policy goals.

As of October 1, 2020, nine states^viii (California, Connecticut, Massachusetts, New Jersey, New York, Oregon, Rhode Island, Washington, and the District of Columbia) will have enacted paid family leave laws, but not all states will have fully implemented the laws yet, such as paying benefits. State laws vary in the weeks of leave offered, percentage of pay provided, job protection, and the funding mechanism.

Paid leave policies to bond with a new child currently offer a range of 4 weeks in Rhode Island to 12 weeks in Connecticut, Massachusetts, New Jersey, Oregon, and Washington.¹⁴ As shown in the table below, California and DC offer 8 weeks of paid leave, and New York offers 10 weeks. Only five states currently have a paid family leave policy of at least 6 weeks and have begun paying benefits (California, New Jersey, New York, Washington, and DC). All of the nine states with a paid family leave policy in place cover sector private employees, with Washington, New Jersey, Oregon, and Massachusetts covering state employees as well.^15,16,17,18 California, the state for which the most evidence exists, does not have job protection through its paid leave policy, but parents can access job protection through simultaneously taking FMLA benefits or applying for leave through the California Family Rights Act.¹⁹ Prior to July 1, 2020, California provided up to 6 weeks of paid leave to eligible families; beginning that month, parents were able to take up to 8 weeks under the paid leave policy, in addition to any time taken through Temporary Disability Insurance.²⁰ New Jersey also expanded its length of paid leave to 12 weeks from 6 weeks on July 1, 2020.⁴²

Some states have enacted less expansive policies that provide paid family leave to some or all state employees, including Arkansas, Delaware, Idaho, Indiana, Kansas, Missouri, North Carolina, New Mexico, Tennessee, and Virginia.^{21,22,23,24,25,26,27,28,29,30}

“**” in the Yes/No column indicates that the state has passed legislation enacting a paid family leave benefit but that the benefit is not yet available.
Policy adoption, generosity and variation data: As of October 1, 2020. State statutes and legislation on paid family leave.
For additional source and calculation information, please go to Methods and Sources.

8. State counts include the District of Columbia.

Method of Review

This evidence review began with a broad search of all literature related to the policy and its impacts on child and family wellbeing during the prenatal-to-3 period. First, we identified and collected relevant peer-reviewed academic studies as well as research briefs, government reports, and working papers, using predefined search parameters, keywords, and trusted search engines. From this large body of work, we then singled out for more careful review those studies that endeavored to identify causal links between the policy and our outcomes of interest, taking into consideration characteristics such as the research designs put in place, the analytic methods used, and the relevance of the populations and outcomes studied. We then subjected this literature to an in-depth critique and chose only the most methodologically rigorous research to inform our conclusions about policy effectiveness. All studies considered to date for this review were released on or before March 31, 2020.

Standards of Strong Causal Evidence

When conducting a policy review, we consider only the strongest studies to be part of the evidence base for accurately assessing policy effectiveness. A strong study has a sufficiently large, representative sample, has been subjected to methodologically rigorous analyses, and has a well-executed research design allowing for causal inference—in other words, it demonstrates that changes in the outcome of interest were likely caused by the policy being studied.

The study design considered most reliable for establishing causality is a randomized control trial (RCT), an approach in which an intervention is applied to a randomly assigned subset of people. This approach is rare in policy evaluation because policies typically affect entire populations; application of a policy only to a subset of people is ethically and logistically prohibitive under most circumstances. However, when available, randomized control trials are an integral part of a policy’s evidence base and an invaluable resource for understanding policy effectiveness.

The strongest designs typically used for studying policy impacts are quasi-experimental designs (QEDs) and longitudinal studies with adequate controls for internal validity (for example, using statistical methods to ensure that the policy, rather than some other variable, is the most likely cause of any changes in the outcomes of interest). Our conclusions are informed largely by these types of studies, which employ sophisticated techniques to identify causal relationships between policies and outcomes. Rigorous meta-analyses with sufficient numbers of studies, when available, also inform our conclusions.

Studies That Meet Standards of Strong Causal Evidence

1. Bailey, M., Byker, T., Patel, E., & Ramnath, S. (2019). The long-term effects of California’s 2004 paid family leave act on women’s careers: Evidence from US tax data (No. w26416). National Bureau of Economic Research. https://www.nber.org/papers/w26416.pdf
2. Baum, C., & Ruhm, C. (2016). The effects of paid leave in California on labor market outcomes. Journal of Policy Analysis and Management, 35(2), 333–356. https://onlinelibrary.wiley.com/doi/epdf/10.1002/pam.21894
3. Bullinger, L. R. (2019). The effect of paid family leave on infant and parental health in the United States. Journal of Health Economics, 66, 101–116. https://doi.org/10.1016/j.jhealeco.2019.05.006
4. Byker, T. S. (2016). Paid parental leave laws in the United States: Does short-duration leave affect women’s labor-force attachment? American Economic Review, 106(2), 242–246. https://www.aeaweb.org/articles?id=10.1257/aer.p20161118
5. Choudhury, A.R. & Polachek, S.W. (2019). The impact of paid family leave on the timing of infant vaccinations (No. 12483). IZA Institute of Labor Economics. https://www.iza.org/publications/dp/12483/the-impact-of-paid-family-leave-on-the-timing-of-infant-vaccinations
6. Das, T. & Polachek, S. W. (2015). Unanticipated effects of California’s paid family leave program. Contemporary Economic Policy, 33(4), 619–635. https://doi.org/10.1111/coep.12102
7. Hamad, R., Mordrek, S. & White, J. S. (2019). Paid family leave effects on breastfeeding: A quasi-experimental study of US policies. American Journal of Public Health, 109(1), 164–166. https://doi.org/10.2105/AJPH.2018.304693
8. Huang, R. & Yang, M. (2015). Paid maternity leave and breastfeeding practice before and after California’s implementation of the nation’s first paid family leave program. Economics and Human Biology, 16, 45–59. https://doi.org/10.1016/j.ehb.2013.12.009
9. Klevens, J., Luo, F., Xu, L., Peterson, C., & Latzman, N. E. (2016). Paid family leave’s effect on hospital admissions for pediatric abusive head trauma. Journal of the International Society for Child and Adolescent Injury Prevention, 22(6), 442–445. http://dx.doi.org/10.1136/injuryprev-2015-041702
10. Lichtman‐Sadot, S., & Bell, N. P. (2017). Child health in elementary school following California’s paid family leave program. Journal of Policy Analysis and Management, 36, 790–827. https://doi.org/10.1002/pam.22012
11. Pac, J., Bartel, A., Ruhm, C., & Waldfogel, J. (2019). Paid family leave and breastfeeding: Evidence from California (No. w25784). National Bureau of Economic Research. https://www.nber.org/papers/w25784
12. Pihl, A. & Basso, G. (2018). Did California paid family leave impact infant health? Journal of Policy Analysis and Management, 38(1), 155–180. https://doi.org/10.1002/pam.22101
13. Stanczyk, A. B. (2019). Does paid family leave improve household economic security following a birth? Evidence from California. Social Service Review, 93(2), 262–304. https://doi.org/10.1086/703138
14. Rossin-Slater, M., Ruhm, C., & Waldfogel, J. (2013). The effects of California’s paid family leave program on mothers’ leave-taking and subsequent labor market outcomes. Journal of Policy Analysis and Management, 32(2), 224–245. https://doi.org/10.1002/pam.21676
15. Bana, S., Bedard, K., & Rossin-Slater, M. (2018). The impacts of paid family leave benefits: Regression kink evidence from California administrative data (No. w24438). National Bureau of Economic Research. https://www.nber.org/papers/w24438.pdf
16. Lee, B., Modrek, S., White, J., Batra, A., Collin, D., & Hamad, R. (2020). The effect of California’s paid family leave policy on parent health: A quasi-experimental study. Social Science & Medicine, 251, 1–8. https://doi.org/10.1016/j.socscimed.2020.112915
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