With a growth in population from 17.5 million in 1964 to 22.3 million in 1973 and 28.6 million in 1985, Colombia was expected to overtake Argentina in the 1990s and resume its nineteenth-century position as the most populous Latin American country after Brazil and Mexico. Between 1951 and 1964 the country had one of the world's highest rates of demographic increase — 3.5 per cent per annum. From 1965 the rate of growth decelerated — in substantial part as a result of a sharp decline in birth-rates (from 40 per thousand in 1960 to 20 per thousand in 1974). By the early 1980s the annual rate had fallen to less than 2 per cent.

This reduced rate of population growth can be associated with urbanization and improved literacy. By the 1980s urban fecundity had fallen to only 55 per cent of the level in the countryside and was in part attributable to explicit policies of birth control, which, despite the power of the Church, had been adopted since the late 1960s. Between 1973 and 1985 the proportion of Colombians under fifteen years of age fell from 43 to 33 per cent. Nevertheless, growth in the under-five age group of 4 per cent per annum, combined with a 4.4 per cent annual increase among five- to fourteen-year-olds, imposed heavy pressures on health, education and housing services during the 1960s and 1970s.