Uruguay's population has grown slowly throughout its history, reaching the 1 million mark early in the twentieth century. In the twentieth century, the rate of population growth declined steadily, however, despite significant amounts of immigration and virtually halted in the 1950s. Registered at over 2 percent in 1916, the annual growth rate had dropped to 1.4 percent by 1937. It continued in the 1.2 to 1.5 percent range until 1960, but in the 1960s population growth averaged only 1 percent annually. In the 1970s, the average annual growth rate was even lower, at 0.4 percent. In the 1981-88 period, annual population growth was 0.7 percent, but in 1990 it was 0.6 percent.

A major contributor to the slow population growth rate was Uruguay's low, and declining, crude birth rate. It fell steadily throughout the first half of the twentieth century, from 38.9 per 1,000 population in the 1900-04 period to 21.1 per 1,000 in the 1945-49 period, where it more or less stabilized through the mid1960s . In the 1980-85 period, the birth rate was 19.5 per 1,000. In 1987 it was estimated at 17.5, and in 1990 it was estimated at 17 per 1,000. (In comparison, the birth rates for Argentina, Brazil, and the United States in 1990 were 20 per 1,000, 26 per 1,000, and 15 per 1,000, respectively.) This relatively low birth rate was usually ascribed to Uruguay's prosperity and the widespread availability of contraception. Given the secularization of Uruguayan society at the beginning of the twentieth century, the influence of the Roman Catholic Church was minor (see Religion , this ch.). The total fertility rate in 1990 was 2.4 children born per woman.

The crude death rate, which had averaged 14 to 15 per 1,000 since the 1895-99 period, began to decline significantly starting in the 1920s. In the 1940s, it reached 10 per 1,000, and it has stayed at approximately this level every since. In 1987 the crude death rate was estimated at 9.5 per 1,000 and in 1990 at 10 per 1,000.

Advances in medicine resulted in longer life expectancy. Uruguay's General Directorate of Statistics and Census noted that overall life expectancy in the 1984-86 period was 71.6 years (68.4 years for men and 74.9 years for women). Estimates in 1990 placed life expectancy for males at seventy years and that for females at seventy-six years. Because Uruguayans were living longer, the population began to age. By the census year of 1963, demographers already were beginning to worry that the rising proportion of the population in retirement might overstrain the country's social security system (see Social Security Pensions , this ch.). The 1975 and 1985 censuses confirmed the acceleration of this aging trend. The trend was aggravated as net immigration, which had characterized Uruguay in the early twentieth century, gave way to net emigration and the exodus in particular of young, well-educated Uruguayans.

Data as of December 1990