A country can never be too rich, too beautiful or too full of people

“Our Country is FULL!” U.S. President Donald Trump recently tweeted.

He was referring to immigrants, but the rhetorical tweet begs the question: Can a country ever be full?

Economists like me have been arguing for centuries about the question but also a closely related one: Is a growing population good or bad?

A country’s ‘carrying capacity’

The first economist to suggest there were limits to how many inhabitants a country could support was Thomas Malthus, who wrote his most famous work, “An Essay on the Principle of Population,” in 1798.

Malthus believed that each country had a “carrying capacity,” a maximum number of people it can support. When the population is above its carrying capacity, it is full.

Thomas Malthus. John Linnell/Welcome Collection, CC BY
Carrying capacity is based on environmental factors, such as the amount of food resources that can be grown on land or harvested from the sea. If Malthus were alive today, he would point out there is a fixed amount of oil in the Earth and a fixed amount of farmland to grow crops. Sooner or later the oil will run out, and if population grows without bound, there will not be enough food to feed everyone.

Malthus’ predictions about what happens after a country rises above its carrying capacity were dire: Disease, famine and wars break out to bring the population back down to a sustainable level. In simple terms, Malthus’ theory was that the population in a country cannot grow indefinitely. Death will constrain it.

This harsh conclusion is one of the reasons people began calling economics the “dismal science.”

Another doomsayer, though not an economist, is author Jared Diamond, whose popular book “Collapse” showed numerous times in history when population growth led to environmental damage that destroyed a society. The damage occurred because ever-increasing population forced people to move onto marginal lands and unsafe lands.

Supporters of Diamond’s ideas point out the problems that occur as an ever-growing population builds homes, businesses and farms in flood zones and seeks shelter in places like the sides of active volcanoes.