In her seminal 1985 paper, Lundberg developed the concept of the added worker effect, which explains countercyclical increases in the labour supply of married women as responses to their husbands' cyclical unemployment.
[11] Together with Elaina Rose, Lundberg finds that the effects of parenthood on the earnings and hours worked of married men and women strongly vary on the continuity of the mother's attachment to the labour force and on the child's gender: if the wife's employment is interrupted, the fall in the hours worked and wages of the wife is partly offset by an increase in the labour supply and earnings of the husband, whereas in the opposite case fathers' hours worked decrease strongly; moreover, all else equal, fathers tend to increase their labour supply and wages substantially more in case of a son than if they have a daughter,[12][13] a finding in line with further work by Lundberg on child gender bias.
In a seminal paper with Robert A. Pollak, Lundberg developed the "separate spheres" bargaining model, wherein spouses don't threaten each other with divorce but rather with the adoption of a non-cooperative separate spheres approach to the marriage, with important implications for marriage market and the distributional consequences of transfer policies.
[17] In line with this view, Lundberg, Pollak and Terence Wales observe that the reallocation of child benefits to wives in the UK was associated with substantial increases in households' expenditures on women's and children's clothing.
In research with Robert Plotnick, Lundberg observes important differences between the responsiveness of Caucasian and Afro-American adolescents' premarital pregnancies, pregnancy outcomes and prenatal marriages to welfare benefits, abortion laws and family planning policies, with Afro-Americans' behaviour being essentially unaffected by these policy variables.
[21] The importance of racial differences in the effects of teenage pregnancies is also reflected by Lundberg and Plotnick's finding (together with Daniel Klepinger) that having a child before age 18 significantly reduces educational attainment only among Afro-Americans, though significant negative effects can also be observed for Caucasians and Hispanics with regard to childbearing before the age of 20.