Stage four of the Demographic Transition Model (DMT) is accomplished when a country's birth and death rates are both low, thus, stabilizing the growth of the total population. Reaching such stage can be attributed to different factors such as a strong economy, universal healthcare systems, increasing employment opportunities for women and a highly educated population.
Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years
