The Demographic transition model (DTM) is a model used to represent the process of explaining the transformation of countries from high birth rates and high death rates to low birth rates and low death rates as part of the economic development of a country from a pre-industrial to an industrialized economy. It is based on an interpretation begun in 1929 by the American demographer Warren Thompson  of prior observed changes, or transitions, in birth and death rates in industrialized societies over the past two hundred years.
Most developed countries are beyond stage three of the model; the majority of developing countries are in stage 2 or stage 3. The model was based on the changes seen in Europe so these countries follow the DTM relatively well. Many developing countries have moved into stage 3. The major (relative) exceptions are some poor countries, mainly in sub-Saharan Africa and some Middle Eastern countries, which are poor or affected by government policy or civil strife, notably Pakistan, Palestinian Territories, Yemen and Afghanistan.