Illustration by Nishant Choksi

In recent years, it’s become a commonplace that American companies are too obsessed with the short term. In the heyday of Bell Labs and Xerox PARC, the argument goes, corporations had long time horizons and invested heavily in the future. But now investors care only about quarterly earnings and short-term stock prices, so companies skimp on R. & D. and waste hundreds of billions propping up their stock with share buybacks. This “tyranny of accountants” has damaged both the long-term prospects of companies and the U.S. economy as a whole.

The latest public figure to embrace this diagnosis is Hillary Clinton. In a speech a couple of weeks ago, she unveiled a solution: changing the capital-gains tax in order to encourage investors to hold stocks longer. Right now, there are only two capital-gains categories: anything held for less than a year is short-term; anything longer is long-term. Clinton’s plan, which would apply only to investors in the highest tax bracket, would expand the definition of short-term to include any investment held for less than two years, and it would create a sliding scale of rates. For every extra year (up to six) that you keep a stock, you pay a lower rate.

The political appeal of the plan is clear. It targets wealthy investors, is friendly to executives, and is aimed at getting companies to spend more money. Unfortunately, it almost certainly won’t work. The simplest reason for this is that the plan would affect only a small slice of the market. Len Burman, a tax expert at the Urban Institute, told me, “The plan’s unlikely to have a major impact on stock prices, since most of the money in the market is controlled by institutions that don’t pay capital-gains taxes, like endowments and pension funds.” Burman also made the point that pushing people to hold stocks they would rather sell is hardly conducive to productive investment. “Even if short-termism is the problem, locking people into unprofitable transactions for long periods of time doesn’t really seem like a great solution,” he said.

Aside from these practical problems, the plan rests on two common but ultimately questionable assumptions. The first is that corporate decision-makers care only about the short term. The second is that it’s the stock market that makes them think this way. These assumptions are widely shared and long-standing, in both business and academe. A famous report from the Council on Competitiveness in the early nineties concluded that, compared with Germany and Japan, the U.S. was greatly underinvesting in the future. In 2005, the C.E.O. of Xerox, Anne Mulcahy, described the pressure from Wall Street for short-term profits as “a huge problem,” and, in a survey of executives that same year, more than half said they would delay valuable new projects in order to boost short-term earnings.

That sounds pretty bad. Yet when you actually look at the numbers the story gets more complicated. There is reason to think that some companies are investing too little in the future. As a whole, though, corporate spending on R. & D. has risen steadily over the years, and has stayed relatively constant as a share of G.D.P. and as a share of sales. This year, R. & D. spending is accelerating at its fastest pace in fifty years and is at an all-time high as a percentage of G.D.P. Furthermore, U.S. companies don’t spend notably less on R. & D. than their international competitors. Similarly with investors: their alleged obsession with short-term earnings is hard to see in the data. Several studies in the nineties found that companies announcing major R. & D. investments were rewarded by the markets, not punished, and that companies with more institutional investors (who typically have shorter time horizons) spent more on R. & D., not less. A 2011 Deutsche Bank study of more than a thousand companies found that those which spent significantly more on R. & D. than their competitors were more highly valued by investors. And a 2014 study of companies that cut R. & D. spending in order to meet short-term earnings goals found that their stocks underperformed after earnings had been announced—hardly what you’d expect if the market cared only about the short term.

Of course, there’s no shortage of investors who are myopic. But the market, for the most part, isn’t. That’s why companies like Amazon and Tesla and Netflix, whose profits in the present have typically been a tiny fraction of their market caps, have been able to command colossal valuations. It’s why there’s a steady flow of I.P.O.s for companies with small revenues and nonexistent earnings. And it’s why the biotech industry is now valued at more than a trillion dollars, even though many of the firms have yet to bring a single drug to market. None of these things are what you’d expect from a market dominated by short-term considerations.

To the extent that companies are underinvesting in the future, the blame lies not with investors but with executives. The pay of many C.E.O.s is tied to factors like short-term earnings, rather than to longer-term metrics, which naturally fosters myopia. That 2014 study of companies that cut R. & D. spending found that the executives responsible saw their pay rise sharply, even though the stock didn’t. If Clinton really wants to deal with short-termism, she’d be better off targeting the way executive compensation works, instead of the way capital gains are taxed. Ultimately, the solution to short-termism isn’t on Wall Street. It’s in the executive suite. ♦