As if Donald J. Trump’s victory wasn’t surprising enough, the economic reaction has been even more stunning. Despite forecasts of a stock market meltdown if he won, the market registered one of its strongest postelection rallies in more than a century. Now the euphoria is spilling into the wider economy, with business confidence skyrocketing and consumer confidence hitting a 15-year high. Much of this excitement is inspired by a growing consensus that Mr. Trump could be the most-business friendly president since Ronald Reagan.

Indeed Mr. Trump’s advisers say that over the next decade, their plans for tax cuts and deregulation could push the average annual growth rate back up to 3.5 percent — the same as during the Reagan presidency. Mr. Trump says the country can grow even faster. His backers dismiss skeptics as defeatists and have insisted there is “no law of nature or economics” that would prevent the United States from reviving the boom of the 1980s.

Only there is such a law. The forces that underlie economic growth have weakened significantly since the Reagan years, worldwide. No nation, no matter how exceptional, can try to grow faster than economic forces allow without the risk of provoking a volatile boom-bust cycle.

The potential growth rate of an economy is roughly determined — and limited — by the sum of two factors: population and productivity. An economy can grow steadily only by adding more workers, or by increasing output per worker. During the Reagan years, both population and productivity were growing at around 1.7 percent a year, so the potential United States growth rate was close to 3.5 percent. In short, Reagan did not push the nation’s economic engine to run faster than it could handle.