found that "employees’ use of leave, and employers’ granting and administration of leave, have achieved a level of stability. Employees actively make use of the intended benefits established by the Act, but appear to have limited knowledge of what the Act specifically entails and covers. At the same time, most employers report that complying with the FMLA imposes minimal burden on their operations, although a subset of employers reported difficulty complying." Although much of the research has been conducted on populations in other countries, Berger et al. found that children in the United States whose mothers return to work within the first 3 months after giving birth are less likely to be breastfed, have all of their immunizations up to date (by 18 months), and receive all of their regular medical checkups; they are also more likely to exhibit behavioral problems by four years of age. Chatterji and Markowitz also found an association between longer lengths of maternity leave and lesser incidence of depression among mothers. In spite of the FMLA's lack of requirements to provide paid leave, the 2012 Department of Labor study found that by that point in time, most employees who were surveyed reported receiving some sort of paid leave, with 48% reported as receiving full pay and another 17% receive partial pay, usually but not exclusively through regular paid vacation leave, sick leave, or other “paid time off” hours. However, despite the FMLA's expansion of rights to take leave, it did guarantee a right to free child care or day care at the federal level. This has encouraged several proposals to create a public system of free child care, or for the government to subsidize parents' costs. Controversy The act was controversial at its passage. Much of the controversy focused on its impact on the business community, and on whether the law should be gender neutral or not. In order to make the law more acceptable, it was argued that the law would reduce abortions. Proponents of the law focused on its benefit to men and children, in order to counter the claim that it was giving women "special treatment". Other controversies focused on whether the leave should be paid or not. The law was finally approved, mandating unpaid gender-neutral leave; nevertheless it was still criticized. Critics of the act have suggested that by mandating various forms of leave that are used more often by female