In addition to the classic Malthusian model, Figure 4.1 in Chapter 4 is also relevant to understanding high-fertility traps. In the diagram, we can take the x-axis to represent (expected) fertility and the y-axis the family’s own fertility decision. The upward-sloping response of own fertility to average fertility may be caused by at least two important factors. If others have high fertility, this may increase the number of formal-sector job seekers without (proportionally) increasing the number of formal-sector jobs. Each family may feel it needs a larger number of children to raise the probability that one child will get a modern job. In addition, families often follow local social norms about fertility and tend to model their own behavior on the behavior of others in their community. If the fertility response curve cuts the 45-degree line from above at least twice, then there are at least two stable equilibria (see Chapter 4), one with high and another with low levels of average fertility.6