When stability was established in the 1920s, birth rates rose and death rates fell. From the 1920s to the 1970s, Mexico was in phase two of the demographic transition with high birth rates and falling death rates. Population growth was rapid in phase two. In the 1970s, Mexico entered the third phase of the demographic transition. In this phase, death rates are relatively stable, and birth rates start to drop markedly.
Family size begins to decrease as the total fertility rate drops.
Population continues to grow, but the percentage rate of increase declines. By the 1970s, Mexico had an urban majority. Traditional attitudes about family size were altering, and the Mexican government dropped many pro-natal policies and began to promote family planning. Mexico will not enter phase four of the demographic transition in this century. The death rate, at 5 per thousand of the population, cannot fall much further, and will tend to rise as the population ages.