The Demographic Transition Model

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The demographic transition model aka the DTM is used to see the population trends of a country. The DTM tracks birth rate and death rate, both of which contribute to the natural increase rate. The natural increase rate or NIR is the birth rate minus the death rate. There are (technically) 5 stages although the last one is theoretical. The first stage has high death and birth rates leaving the natural increase rate stagnant. Almost no country is in this stage. In the second stage the death rates drop and the birth rates stay very high leaving natural increase high. Most sub-Saharan countries are in this stage. In the third stage birth rates drop and death rates stay the same making natural increase go down. In stage four both birth and death rates remain the same as natural increase is at zero. This is where the US and other more developed countries are. Stage 5 is purely theoretical as no country has reached it yet but it is a trend that might continue. In this stage the death rate goes up as more old people die and the birth rate goes down. Japan is a country on the verge of this stage.