Lessons > The Demographic Transition > Step 2
The overall population growth rate is only one of the differences among countries in different stages of the transition. The age-based population structure is also greatly affected. Note that the average fertility rate for women in the United States, for example, is 2.06, which is a replacement rate, i.e., enough children are born to replace their parents, with the additional small percentage representing those who die before reaching adulthood. The death rate likewise remains a constant percentage for each age group. Now look at the population pyramid for all of the countries in turn. Compare the pyramid structure of the countries that you found to be late in the transition to those that are earlier in the transition.