Who can summarize this income inequality in the united states has reached its highest peak since the great depression (link is external). americans in the top 1 percent of earners currently make a staggering 40 times as much (link is external) as the bottom 90 percent. furthermore, in 1978 the top 0.1 percent of the population laid claim to 7 percent of the nation’s wealth. by 2012, that amount had increased to 22 percent (link is external). across industrialized nations, income inequality has been linked to an array of harmful outcomes, including higher rates of debt (link is external), crime (link is external), mental illness (link is external), and even mortality (link is external). to better understand such correlations, researchers are investigating how economic inequality might influence the behavior of those who are aware of it.

Read this excerpt from "edward jenner and the history of smallpox and vaccination.” smallpox was introduced to europe sometime between the fifth and seventh centuries and was frequently epidemic during the middle ages. the disease greatly affected the development of western civilization. the first stages of the decline of the roman empire (ad 108) coincided with a large-scale epidemic: the plague of antonine, which accounted for the deaths of almost 7 million people. the arab expansion, the crusades, and the discovery of the west indies all contributed to the spread of the disease. unknown in the new world, smallpox was introduced by the spanish and portuguese conquistadors. the disease decimated the local population and was instrumental in the fall of the empires of the aztecs and the incas. similarly, on the eastern coast of north america, the disease was introduced by the early settlers and led to a decline in the native population. before it reached the new world, smallpox played a role in