In Niger, whose growth rate is 3.4 percent per year, 49 percent of the population is younger than age 15, so Niger can expect a baby boom when those children reach reproductive age. Even if fertility rates fall sharply, the population will continue to grow for some years as this younger generation starts families. Notice that there are more older females than males in Sweden because of differences in longevity between the sexes. A population that has recently entered a lower growth rate pattern, such as Singapore, has a bulge in the age classes for the last high-birth-rate generation.