[The changing age distribution of the Brazilian population in the first half of the 21st century].

Brazil is currently in an advanced stage of both the mortality and fertility transitions, which allows one to confidently forecast the age distribution and population size over the next four decades. Whereas the elderly population (> or=65 years) will increase at high rates (2-4% per year), the young population will decline. According to United Nations projections, the elderly population will increase from 3.1% of the population in 1970 to 19% in 2050. Meanwhile, within the young and adult populations, growth rates will vary among different age groups, ranging from negative to positive values. The changing age distribution of the Brazilian population brings opportunities and challenges that could lead to serious social and economic issues if not dealt with properly in the coming decades.