Bregman next looks at prosperity in different regions of the world. While the countries of the Global North enjoy historic levels of prosperity, much of the Global South remains mired in desperate poverty, hunger, and disease. Wealthier countries have contributed large sums in foreign aid, but the effectiveness of this aid is hard to gauge. Aid may have had a great impact, in which case more aid would be even more beneficial, or may have harmed those it intended to help, in which case more aid could make things worse. Research on the subject has typically failed to conduct controlled trials to establish a causal relationship between how a certain method of treatment affects a particular group. Instead, the argument has focused on the relative merits of either providing greater resources or building local capacity. French professor Esther Duflo has pioneered a new approach of testing similar target audiences using various methods in order to arrive at more definitive conclusions. This approach helps move beyond the “rational actor” model that sees humans as cool calculators and instead seeks to understand how different conditions encourage different attitudes and behaviors. Controlled tests are not always possible, and they cannot address major structural problems.