The graph shows changing population statistics during the early part of the twentieth century. A line graph showing African American Population by Region, 1900 to 1930 comparing the Midwest to Northeast. X axis is years 1900, 1910, 1920, 1930. Y axis is Population in increments of 500,000 starting at 0 and ending at 1,500,000. In 1900 and 1910 both regions were around 500,000. In 1920 both grew to around 750,000, and in 1930 both were close to 1,250,000.

By the 1930s the African American population of the Midwest and Northeast

had more than tripled since 1900.
had more than doubled since 1900.
had increased by half since 1900.
had remained the same since 1900.

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.