Thomas Robert Malthus (1766–1834) predicted that population would rise relative to the supply of natural resources necessary to feed people at subsistence levels over the long term. In 1968, when the world population was 3.5 billion, the biologist Paul Ehrlich echoed Malthus in the best-selling book The Population Bomb, which predicted impending disastrous global consequences from overpopulation.

Centuries after the death of Malthus, many Malthusians continue to warn about excessive population growth in the world. Are they right?

Global demographic data, especially data from poor countries, would seem to vindicate Malthus. Between 1968 and 2017, world population more than doubled to 7.5 billion and the fertility rate in developing countries was approximately three times the rate in developed countries. For example, Nigeria, with a total population of 191 million in 2017, had a fertility rate of 5.5, relative to the world average of 2.4. For many people in poor countries, especially in sub-Saharan Africa and the Middle East, hunger remains a serious problem, as Malthus expected.

Population in the developing world / However, Malthus and Malthusians missed the dramatic demographic change that has occurred in some developed countries and threatens to occur in many others. Total population is declining in Russia, Japan, and Italy: Russia’s decline began in the 1990s, Japan has been declining for the last eight years, and Italy has been declining for the last four. The negative effect of low fertility on Italian population growth has been exacerbated by net emigration of younger Italians. Economic growth in those three countries has been slow because of reduction in their labor force and productivity. Japan has had two decades of near zero economic growth; Italy’s gross domestic product per capita, adjusted for inflation, was lower in 2018 than it was in 2000.

In many other developed countries, population would have declined in recent years were it not for immigration. Fertility rates in most rich countries have been below the replacement level of 2.1 for some time. In 2017, the average fertility rate for the rich countries of the Organization for Economic Cooperation and Development was 1.7. In the European Union it was 1.6 and the United States was 1.7. Fertility rates in the prosperous countries of Asia have also fallen below replacement level, including 1.4 for Japan, 1.4 for South Korea, 1.2 for Singapore, and 1.6 for China.

Migration / Fertility rates nearly three times as high in developing countries than developed countries have persisted for some time, with the result that populations in rich countries are much older. The percentage of the population over age 65 in 2017 was six times as great in developed countries than in developing countries. In 2017, Japan had the oldest population, with 28% over age 65 compared to the world average of 9%. Italy was next highest at 23%. The United States was at 16% and rising.

Migration from poor to rich countries has been stimulated by Great Divergences in fertility rates and ages of populations. Emigration from poor countries has also been magnified by violence in failed states such as Libya, Nigeria, and Guatemala.

The massive migration from the developing world to the developed world has resulted in organized opposition in receiving countries and the rise of populist or economic nationalist movements and political leaders such as Donald Trump in the United States, Brexit supporters in Great Britain, Victor Orban in Hungary, and the Law and Justice Party in Poland. Opponents of immigration in Germany have punished Angela Merkel’s Christian Democratic Union for its liberal policies on immigration. The proposed border wall on the U.S.–Mexican border is a graphic symbol of opposition to immigration.

Immigrants are a convenient scapegoat employed by populist politicians, but technology and trade shocks explain much of the labor displacement in the receiving countries. In some countries, natives may not oppose all immigrants, but rather those who are “culturally different.” For example, the Polish government has strongly opposed European Commission encouragement for member nations to accept Muslim immigrants, but Poland has accepted large numbers of neighboring Ukrainians.

Not all countries have resisted immigration. Prior to 1973, Australia was known for its restrictive “White Australia” policy that limited immigration to people of European origin. Major reform has transformed Australia from a country largely closed to immigrants to a country with one of the highest percentages of foreign-born residents (29%) in the world. Australian immigration policy has favored skilled immigrants and foreign students, and the result has been rapid economic growth.

Demographic developments in distant parts of the world can have powerful economic and political effects in other countries. Most receiving countries have reacted by raising barriers to immigration, but Australia has demonstrated that encouraging selective immigration can be used to avoid possible negative effects of population decline. Malthus has warned us about the dangers of too many people. Can there also be too few?