It is the most significant economic and sociological challenge we face. It’s worldwide. It has been worsening for decades. And there is no reason to expect the trend to change.

People are not having as many children as they used to. Almost all the developed countries are below the “replacement rate” of 2.1 children per woman of childbearing age. (The U.S. number is 1.6.) Overall, two-thirds of the world’s population now lives in countries below the replacement rate.

If a country is below the replacement rate, its population will eventually peak and begin to decline. In fact, South Korea, Japan, and Italy are already experiencing shrinking populations.

What difference does that make?

A shrinking population means that per capita production (and therefore, consumption per person) will be lower than otherwise. But the bigger problem concerns elderly entitlements. Income and medical care for retirees are mainly financed by worker taxes on a pay-as-you-go basis all over the world. As the ratio of dependents to workers rises, countries will face an unending financial crisis.

There are four reasons why this is happening.

The opportunity cost of motherhood.

For most of the 20th century, a typical woman aspired to be a housewife and mother. In the interim, she chose occupations that accommodated her husband’s career. Teaching, nursing and secretarial work, for example, are in demand almost everywhere.

In the modern era, things are different. Women have entered such fields as medicine, law, business and STEM in large numbers. Today, a majority of medical school students and law school students are female.

These changes mean that the opportunity cost of being a mother is much higher than it used to be. Dropping out of the labor market to raise children........

© Townhall