Across the United States the average age of first time mothers has increased across all races and ethnicities. Over the past four decades the average age of first time mothers has increased from 21 years old in 1970 to 26 years old in 2014. According to the National Centre for Health Statistics this can be attributed to a decline in teenage pregnancies and an increase in women having children over the age of 30. Mothers are also having their children closer together, which statistician Brady E. Hamilton argues is a result of postponing their first births, noting that this can lead to smaller families and smaller overall population growth. Hans-Peter Kohler, Professor of sociology at the University of Pennsylvania, suggests that economics also plays an important role in people’s decisions as they tend to delay making commitments in recessions. Read more here.