During the first half of the twentieth century, both mortality rates and the incidence of infectious diseases declined, due primarily to public health measures and a higher standard of living. Developments in surgery and drug therapy improved medical care and increased the amount of specialization among physicians. On the other hand, fewer physicians were available to care for the sick because of a decline in the per capita number of medical school graduates. The urban poor continued to receive most of their care from outpatient departments in public and private hospitals, while a growing number of the middle classes became paying inpatients in private hospitals. Hospitals expanded their educational activities to include internships and residency programs. In the first half of the century, physicians became less accessible to much of the population. The number of physicians per capita decreased substantially from 1900 to 1930 and remained at that level until 1950. The greatest impact of this decline occurred in rural areas: between 1906 and 1923, communities of under 5,000 population experienced about a 25 percent reduction in the physician-population ratio, while cities of 50,000 or more experienced a decline of less than 8 percent. Young physicians especially preferred the cities. In 1906 in communities of fewer than 1,000 persons, the proportion of graduates from 1901 to 1905 who practiced in those communities exceeded the proportion of all physicians who practiced in those communities by a ratio of 1.17 to 1. By 1923 in the same size communities, the proportion of graduates of the classes of 1916 to 1920 who practiced there compared to the proportion of all physicians who practiced there dropped to a ratio of 0.58 to 1. Thus rural communities changed from locations preferred by younger physicians to locations avoided by them. The same ratio in cities of over 100,000 population increased from 0.99 to 1 in 1906 to 1.36 to 1 in 1923, which indicated the growing popularity of large cities for young physicians. Several factors accounted for the preference of physicians for towns and cities. Urban physicians earned more than rural ones and had greater opportunities to Specialize.