3 thoughts on “Demographic transition (Our World in Data)

  1. shinichi Post author

    World Population Growth

    by Max Roser, Hannah Ritchie, Esteban Ortiz-Ospina and Lucas Rodés-Guirao

    Why is rapid population growth a temporary phenomenon?

    The demographic transition

    Population growth is determined by births and deaths and every country has seen very substantial changes in both: In our overview on how health has changed over the long run you find the data on the dramatic decline of child mortality that has been achieved in all parts of the world. And in our coverage of fertility you find the data and research on how modern socio-economic changes – most importantly structural changes to the economy and a rise of the status and opportunities for women – contributed to a very substantial reduction of the number of children that women have.

    But declining mortality rates and declining fertility rates alone would not explain why the population increases. If they happened at the same time the growth rate of the population would not change in this transition. What is crucial here is the timing at which mortality and fertility changes.

    The model that explains why rapid population growth happens is called the ‘demographic transition’. It is shown in the schematic figure. It is a beautifully simple model that describes the observed pattern in countries around the world and is one of the great insights of demography.9

    The demographic transition is a sequence of five stages:

    • Stage 1: high mortality and high birth rates. In the long time before rapid population growth the birth rate in a population is high, but since the death rate is also high we observe no or only very small population growth. This describes the reality through most of our history. Societies around the world remained in stage 1 for many millennia as the long-run perspective on extremely slow population growth highlighted. At this stage the population pyramid is broad at the base but since the mortality rate is high across all ages – and the risk of death is particularly high for children – the pyramid gets much narrower towards the top.
    • Stage 2: mortality falls but birth rates still high. In the second phase the health of the population slowly starts to improve and the death rate starts to fall. Since the health of the population has already improved, but fertility still remains as high as before, this is the stage of the transition at which the size of the population starts to grow rapidly. Historically it is the exceptional time at which the extended family with many (surviving) children is common.
    • Stage 3: mortality low and birth rates fall. Later the birth rate starts to fall and consequentially the rate at which the population grows begins to decline as well. Why the fertility rate falls is a question that we answer here. But to summarize the main points: When the mortality of children is not as high as it once was parents adapt to the healthier environment and choose to have fewer children; the economy is undergoing structural changes that makes children less economically valuable; and women are empowered socially and within partnerships and have fewer children than before.
    • Stage 4: mortality low and birth rates low. Rapid population growth comes to an end in stage 4 as the birth rate falls to a similar level as the already low mortality rate. The population pyramid is now box shaped; as the mortality rate at young ages is now very low the younger cohorts are now very similar in size and only at an old age the cohorts get smaller very rapidly.
    • Stage 5: mortality low and some evidence of rising fertility. The demographic transition describes changes over the course of socio-economic modernization. What happens at a very high level of development is not a question we can answer with certainty since only few societies have reached this stage. But we do have some good evidence – which we review here – that at very high levels of development fertility is rising again. Not to the very high levels of pre-modern times, but to a fertility rate that gets close to 2 children per woman. What level exactly the fertility rate will reach is crucial for the question of what happens to population growth in the long run. If the fertility rate stays below 2 children per woman then we will see a decline of the population size in the long run. If indeed the fertility rate will rise above 2 children per woman we will see a slow long-run increase of the population size.

    Empirical evidence for the demographic transition

    Rapid population growth is a temporary phenomenon

    If fertility fell in lockstep with mortality we would not have seen an increase in the population at all. The demographic transition works through the asynchronous timing of the two fundamental demographic changes: The decline in the death rate is followed by the decline in birth rates.

    This decline in the death rate followed by a decline in the birth rate is something we observe with great regularity and independent of the culture or religion of the population.

    The chart presents the empirical evidence for the demographic transition for five very different countries in Europe, Latin America, Africa, and Asia. In all countries, we observed the pattern of the demographic transition, first a decline in mortality that starts the population boom and then a decline in fertility which brings the population boom to an end. The population boom is a temporary event.

    In the past, the size of the population was stagnant because of high mortality. Now country after country are moving into a world in which the population is stagnant because of low fertility.

  2. shinichi Post author




    人口転換(demographic transition)とは、社会の近代化にともない、人口の自然増加の形態が多産多死型から多産少死型へ、さらに少産少死型へと変化することである。







  3. shinichi Post author

    第3節 先進国の出生率の動向











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