A growth rate of 3.8% sounds small. Compounded for three decades it took Niger from about 8 million people to 24 million, while the land, the schools, the clinics and the wells stayed much as they were. Advance the year and watch how many people share each school and well.
In Niger the land and services stay fixed while the population doubles every 18 years, so the challenge of rapid growth is measured in people per service, not in people alone.