published a study of lifespans and nutrition from about a century before Malthus to the 19th century that examined European birth and death records, military and other records of height and weight that found significant stunted height and low body weight indicative of chronic hunger and malnutrition. He also found short lifespans that he attributed to chronic malnourishment which left people susceptible to disease. Lifespans, height and weight began to steadily increase in the UK and France after 1750. Fogel's findings are consistent with estimates of available food supply. Evidence supporting Malthusianism today can be seen in the poorer countries of the world with booming populations. In East Africa specifically, experts say that this area of the world has not yet escaped the Malthusian effects of population growth. Jared Diamond in his book Collapse (2005), for example, argues that the Rwandan Genocide was brought about in part due to excessive population pressures. He argues that Rwanda "illustrates a case where Malthus's worst-case scenario does seem to have been right." Due to population pressures in Rwanda, Diamond explains that the population density combined with lagging technological advancements caused its food production to not be able to keep up with its population. Diamond claims that this environment is what caused the mass killings of Tutsi and even some Hutu Rwandans. The genocide, in this instance, provides a potential example of a Malthusian trap. Theory of breakout via technology Industrial Revolution Some researchers contend that a British breakout occurred due to technological improvements and structural change away from agricultural production, while coal, capital, and trade played a minor role. Economic historian Gregory Clark, building on the insights of Galor and Moav, has argued, in his book A Farewell to Alms, that a British breakout may have been caused by differences in reproduction rates among the rich and the poor (the rich were more likely to marry, tended to have more children, and, in a society where disease was rampant and childhood mortality at times approached 50%, upper-class children were more likely to survive to adulthood than poor children.) This in turn led to sustained "downward mobility": the descendants of the rich becoming more populous in British society and spreading middle-class values such as hard work and literacy. 20th century After World War II, mechanized agriculture produced a dramatic increase in productivity of agriculture and the Green Revolution greatly increased crop yields, expanding the