Married women are working more in the US. Indeed the rise is so dramatic that it constitutes one of the most notable economic phenomena of the twentieth century in the US. The trend is particular prominent for women with young children. These changes have a myriad of effects on the economy and society ranging from the care of young children and the nature of the family to the structure of income taxation and labour market flexibility. It has produced a revolutionary change in women's economic role.
The explanations for these changes in women’s working lives are as diverse as its implications. Everything from women’s liberation and invention of the vacuum cleaner has been cited as causes.1 Our recent research suggests that progress in medical technologies related to motherhood played a critical role in this process.2
Medicine, motherhood and the labour force
Motherhood takes a lot of time, even today. Until the early decades of the twentieth century, however, it occupied a very considerable fraction of a woman’s lifetime. A typical woman in 1920 had a life expectancy of 55 years (at age 10). She married at age 21 and had on average more than 3 children, with the first birth at age 23 and the last at 33. Her total number of pregnancies was higher than the number of births, given the high fetal mortality rate. In total, she would be pregnant for 34% of the time during her fertile years.
Health risks in connection to childbirth were severe. The pre- and post-partum phases, as well as labour, were associated with considerable suffering that could lead to physical disability and, in the extreme, death. One mother died for each 125 living births in 1920. The four main causes of death were septicemia (40%), toxaemia (25%), trauma (10%) and hemorrhages (10%). At a rate of 3.4 pregnancies per woman, the compounded risk of death in childbirth was 2.7% or 1 in 37, a very considerable number. Add to this that, for every maternal death, twenty times as many mothers suffered different degrees of disablement annually (Munro, 1933). Indeed, infection, toxemia, and trauma were also the main causes of maternal morbidity. The duration of the corresponding disablement ranged between 7 months and 7 years.
An additional factor to consider is that until the early decades of the 20th century most infants were breast fed by their mothers for the first year of life. In 1920 the average woman would be nursing for 33% of the time between age 23 and 33 – a very time-intensive activity. The average time required to breast-feed one child based on infant feeding charts ranges between 14 and 17 hours per week for the first 12 months. This means that on average women would spend 35% to 43% of a 40-hour workweek nursing.
Not surprisingly, these biological demands significantly hindered women's ability to participate in the labour force. This in turn substantially weakened their incentives to invest in marketable skills. Only 9% of married women were in the labour force in 1920, and only 3% among those with preschool children. Starting in the 1930’s there were significant advancements in medical “technologies” related to motherhood. This progress was critical to the rise in married women's labour force participation. The associated reduction in physiological constraints enabled married women with children to enter the labour force and provided an incentive to invest in market skills, potentially narrowing gender earnings differentials.
Two dimensions of medical progress reduced the time spent by women in reproductive duties. The first corresponds to scientific and medical advancements that generated a decline in maternal mortality and morbidity. Leading examples are the introduction of sulfa drugs and antibiotics that dramatically decreased mortality risk from sepsis, blood banking that reduced the risk from haemorrhages, and standardisation of obstetric interventions that brought the incidence of trauma during labour to a minimum. These same advancements also contributed to a fall in fetal deaths and the consequent decline in the number of pregnancies for given fertility. The second dimension is the development and commercialisation of a ‘humanised’ infant formula, which reduced women's comparative advantage in infant feeding by providing an effective breast milk substitute. Medical Progress in this area was largely exhausted by the mid 1950s.
Our quantitative analysis suggests that these medical improvements were indeed a powerful force. They are essential to account for the threefold increase in the labour force participation of married women with children between 1920 and 1950. Improvements in household technologies, such as the introduction of time saving appliances, advocated by Greenwood, Seshadri and Yorugoklu (2005) play an important role between 1950 and 1970.
Our simulations predict that the labour force participation rate of married women should be the same as men’s and that the gender wage gap should have virtually disappeared by 1970. In practice, the participation of married mothers of school age children was approximately equal to 46%, compared with 95% for men, and the ratio of female to male earnings was still hovering around 60%. While technological progress is the only force at work in our model, in reality a variety of offsetting factors were at work. Among those, a very important one until the 1950s was the presence of “marriage bars,” consisting in the practice of not hiring married women or dismissing female employees when they married. Marriage bars were prevalent and pervasive in teaching and clerical work, which accounted for approximately half of single women's employment between 1920 and 1950.3 Cultural forces may also have played an important role in slowing down the increase in women's labour force participation.4
Discrimination in the labour market could be another important factor. Based on recent data, approximately 10% of the gender difference in earnings cannot be accounted for by observables related to productivity. Moreover, despite the fact that women have closed the gap with men in education and professional qualifications, they are still largely under-represented in the higher ranks and still bear the lion's share of home responsibilities. In our 2006 paper5, we show that statistical discrimination amplifies any gender differences in earnings resulting from women's unique biological role. It can also provide a rationale for the persistence of the inequality in earnings and in the household division of labour across genders.
The mechanism works as follows. If employers believe women to be mostly responsible for home work, they will expect them to apply less effort on the job and offer them low tier positions with lower earnings. This makes it efficient for households to assign wives a greater share of home responsibilities. The potential self-fulfilling nature of this mechanism may account for the slow decline of the gender gap in wages and home responsibilities, despite the medical advancements that reduced women's comparative advantage in home production.
One important lesson from this analysis is that gender equality in the labour market is intimately linked to equality in the household division of labour. Policies aimed at reducing gender disparities in earning opportunities are likely to fail if they do not include provisions to reduce women's contribution to home production relative to men.
Many countries are discussing the introduction of more generous maternal leave policies to help women reconcile their maternal and professional roles and reduce their disadvantage with respect to men. Our analysis suggests that such policies may well be counter productive. Generous maternal leave policies reinforce the division of labour that underlies the mechanism by which women are offered lower wages. This is likely to further depress women's professional advancement. Sweden seems to have moved in the right direction with the introduction of a father's month requirement that compels fathers to take at least 30 days of parental leave. By directly reducing the gender asymmetries in the allocation of parental responsibilities, this policy decreases the potential for statistical discrimination that leads to gender inequalities in wages.
1 See, for example, Greenwood, Jeremy, Ananth Seshadri, and Mehmet Yorugoklu, 2005. Engines of Liberation. The Review of Economic Studies 72: 109-133.
2 Albanesi, Stefania and Claudia Olivetti, 2007. Gender Roles and Technological Progress. NBER WP 13179.
3 Goldin, Claudia, 1990. Understanding the Gender Wage Gap: An Economic History of American Women. Oxford University Press.
4 Fernandez, Raquel and Alessandra Fogli, 2005. Culture: An Empirical Investigation of Beliefs, Work and Fertility. NBER WP 11268.
5 Albanesi, Stefania and Claudia Olivetti, 2006. Home Production, Market Production, and the Gender Wage Gap: Incentives and Expectations. NBER WP 12212.