A double burden (also called double day, second shift, and double duty) is the workload of people who work to earn money, but who are also responsible for significant amounts of unpaid domestic labor. This phenomenon is also known as the Second Shift as in Arlie Hochschild's book of the same name. In couples where both partners have paid jobs, women often spend significantly more time than men on household chores and caring work, such as childrearing or caring for sick family members. This outcome is determined in large part by traditional gender roles that have been accepted by society over time. Labor market constraints also play a role in determining who does the bulk of unpaid work. Efforts have been made to document the effects of this double burden on couples placed in such situations. Many studies have traced the effects of the gendered division of labor, and in most cases there was a notable difference between the time men and women contribute to unpaid labor. Unequal work burdens around the world In the industrialized world Pre-World War II The traditional female homemaker–male breadwinner model characterized female employment prior to World War II. At the turn of the 20th century in the continental United States, only 18 percent of women over the age of 15 reported receiving income non-farm employment. These women were typically young, single, white, and native-born. In contrast, married women in the non-farm labor force were "predominantly blacks or immigrants and very poor". Working mothers often exited the labor force once their children were old enough to earn money. The outpouring of occupational opportunities in the early 1920s, such as in "cafeterias, nurseries, laundries and other facilities seemed to release women from domestic chores and freed them to participate fully in the sphere of production." This migration of women into the workforce shook the traditional ideology of gender roles, but importantly, it was the catalyst to the double burden becoming noticeable. The 1930s "encouraged women to fulfill what Stalin termed the "great and honorable duty that nature has given" them. Evident in the Soviet Union, "an officially sponsored cult of motherhood, buttressed by anti-abortion legislation" accompanied by a "depression of living standards" led to industry's immense demand for laborers which got women into the industrial workforce in unprecedented numbers". Urban women thus found themselves assuming the "double burden" (also known as the "double shift") of waged