Every time our tastes as consumers change, we alter the way we spend our money. The number of jobs producing things that we lose our taste for, such as cigarettes, decreases, while the number of jobs producing things that we now have a greater fancy for, such as exercise gear, increases.

Perhaps the major source of job destruction and creation is technological innovation. In the early 1900s automobiles famously destroyed jobs for buggy-whip makers and blacksmiths. Starting in the 1980s, personal computers and email killed jobs for stenographers and document deliverers. Today, A.T.M.s and online banking apps are eliminating jobs for bank tellers.

Yet despite these and innumerable other innovations that caused the demise of particular jobs, the number of jobs in the United States economy is today higher than ever — and contrary to popular myth, the earnings of ordinary Americans recently hit an all-time high.

The reason is that job destruction in a market economy is also job creation. When consumers buy less of a particular product, they spend or invest more money elsewhere, thus creating not only new and better products but also new jobs. Consumers’ freedom to change how they spend their money prompts entrepreneurs and investors to produce things that consumers value most highly, and to do so as efficiently as possible. The result is economic growth.

Fears of losing jobs to trade are inconsistent with our larger embrace of innovation and competition. More ominously, given that trade-induced job losses are a tiny portion of all job losses, such fears are wildly overblown — so much so that they now have America and the world on the brink of a potentially calamitous trade war.

And all for naught. President Trump’s protectionism will simply not create the multitude of jobs that its champions predict. Far worse, however, is the fact that the longer we tolerate this hostility to one particular source of economic change and growth, the more likely we are to grow hostile to technological innovation and other more significant sources of economic change and growth. And it would then become impossible to make America great again.