However, the demographic significance of polygyny extends beyond its direct impact on the proximate determinants of fertility. Nyblade and Menken suggested in 1993 that polygyny may be indicative of adherence to traditional decision-making patterns in the family. Using DHS data they show that, in Kenya, after controlling for other characteristics of the couple, women in polygynous unions are less likely to use contraception than other women. They are relatively unlikely to have discussed contraception with their husband and are less likely to believe that he approves of family planning. The results confirm that polygyny is more prevalent at long marital durations.
Men are much more likely to take another wife if their first wife is infertile.
Because some men take a second wife as an alternative to divorce, the proportion of first wives who are in their first marriage is relatively high. In contrast, higher-order wives are relatively likely to have been married before or to have married for the first time relatively late. Lesthaeghe et al. The former finding is repeated at the individual level in four countries but not Kenya. Ethnicity affects polygyny in a complex way in eastern Africa but is unimportant in Ghana and Senegal.