President Biden’s debate meltdown vividly demonstrated that cognitive and other skills decline with age. But a combination of demographic trends and federal fiscal irresponsibility make it imperative that America make better use of its senior citizens’ productive skills. Not all old people lose it like Mr. Biden. Henry Kissinger was writing important books well into his 90s, and Konrad Adenauer served ably as West Germany’s chancellor until he was 87. Several frequent contributors to these pages are older than Mr. Biden, including Lance Morrow (84), Phil Gramm (82), Joseph Epstein (87) and me (83).

The American population is aging rapidly. In the middle of the last century, there were almost eight working-age (16 to 65) Americans for everyone over 65. I estimate that by 2050 that ratio will shrink to 3 to 1. Hence the need for occupationally capable older citizens to work longer.

That’s already happening to some extent. The proportion of workers over 65 is increasing, and the Bureau of Labor Statistics projects that the median working age of all workers will have risen by nearly three years between 2002 and 2032.

As the standard of living rises over time, shouldn’t it become more affordable for older workers to retire, leaving the production of goods and services to the young? But the supply of young people is shrinking. The number of live births in the U.S. declined from 4.3 million in 1960 to 3.6 million last year, a 15% drop, even though the U.S. population nearly doubled during the same period. In the middle of the last century, the average life expectancy at birth in the U.S. was 67, compared with about 78 today. These trends are present worldwide, with planetary population projected to fall before the end of this century.

American public policy, as manifested in the positions of both major political parties, seems totally oblivious to these challenges. The federal government is behaving more irresponsibly than ever, having spent more than it receives in revenues every single year for well over two decades, so that interest payments on the $35 trillion national debt now exceed spending on national defense. Congressmen and presidents resemble alcoholics, drug addicts or unruly teenagers whose unregulated behavior requires significant outside modification. It’s time to revisit a federal balanced-budget constitutional amendment such as is found in most states.

One way to help alleviate the problem of an inadequate number of younger workers is to import them—to increase the inflow of highly productive immigrants. The financial imperatives of a nearly bankrupt Social Security system will also likely force us to raise the standard retirement age, meaningfully increase payroll taxes, reduce pensions, trim Medicare or maybe all of the above. In the meantime, let’s celebrate those who are able to work beyond 65. I’m happy to be among the octogenarians for whom working adds to the quality of life while helping relieve a growing national problem.