When did the us enter stage 4 of the demographic transition model?

The United States entered Stage 4 of the Demographic Transition Model in the mid-20th century, around the 1950s. This stage is characterized by low birth and death rates, leading to a stable population. Factors contributing to this transition include improved healthcare, access to contraception, and changing social norms regarding family size. As a result, the U.S. has experienced population aging and urbanization typical of Stage 4.