There are complex and diverse reasons that people enter into age-disparate relationships, and a recent review in the Journal of Family Theory and Review showed vast differences across contexts.[22] Explanations for age disparity usually focus on either the rational choice model or the analysis of demographic trends in a society.[2] The rational choice model suggests that people look for partners who can provide for them in their life (bread-winners); as men earn more as they get older, women will therefore prefer older men.[12] This factor is diminishing as more women enter the labor force. The demographic trends are concerned with the sex ratio in the society, the marriage squeeze, and migration patterns.[12] Another explanation concerns cultural values: the higher the value placed in having children, the higher the age gap will be.[3] Yet Canadian researchers have found that age-disparate couples are less likely to have children than similarly aged ones.[23] As people have chosen to marry later and remarriage becomes more common, the age differences between couples have increased as well.[12][5]