What countries are in stage 4 of the demographic transition model

The correct answer is - the developed countries.

The developed countries are the ones that in the fourth stage of the demographic transition model. This demographic transition model suggests that the birth rates are very low, the life expectancy very high, resulting in an aging population, and later in decline of the population.

That is exactly what is happening in the developed countries. We can take Japan as a perfect example. It is one of the most developed countries in the world. It has a very strong economy, excellent infrastructure, the institutions are accessible for all the people, the health care is on an excellent level. Despite all those positives, there's more and more people that decide to not get married, to not have children, and live a single life, or the ones that do get married tend to have one child in lot of cases. The life expectancy is the second highest in the world. This results in a demographic pyramid that is losing the shape of a pyramid, the lower part of it is becoming smaller and smaller, while the middle and upper part of the pyramid are constantly growing. This will lead to a quick decline in the population of the country in the coming decades.