There is an economic mystery I’ve been struggling to understand for quite some time, and I’m not the only one who’s confused: Among financial experts, it is often referred to as a conundrum, a paradox, a puzzle. The mystery is as follows: Collectively, American businesses currently have $1.9 trillion in cash, just sitting around. Not only is this state of affairs unparalleled in economic history, but we don’t even have much data to compare it with, because corporations have traditionally been borrowers, not savers. The notion that a corporation would hold on to so much of its profit seems economically absurd, especially now, when it is probably earning only about 2 percent interest by parking that money in United States Treasury bonds. These companies would be better off investing in anything — a product, a service, a corporate acquisition — that would make them more than 2 cents of profit on the dollar, a razor-thin margin by corporate standards. And yet they choose to keep the cash.

Take, for example, Google. Its new parent company, Alphabet, is worth roughly $500 billion. But it has around $80 billion sitting in Google’s bank accounts or other short-term investments. So if you buy a share in Alphabet, which has sold for roughly $700 lately, you are effectively buying ownership of more than $100 in cash. With $80 billion, Google could buy Uber and its Indian rival Ola and still have enough left over to buy Palantir, a data-mining start-up. Or it could buy Goldman Sachs outright or American Express or most of MasterCard; it could buy Costco or eBay or a quarter of Amazon. Surely it could use those acquisitions to earn more than 2 cents on the dollar.

This strange vogue for corporate hoarding seems to have begun around the turn of the millennium. General Motors is perhaps the most extreme: It now holds nearly half its value in cash. Apple holds more than a third. These numbers are maddening on their face. If the companies spent their savings, rather than hoarding them, the economy would instantly grow, and we would most likely see more jobs with better pay. In the 1990s, when companies saved far less of their profits, they built new factories, bought new buildings. In part because of all that corporate spending, the 1990s were a period of low unemployment and high growth. Remarkably, the United States government was able to tax all that productive corporate behavior so much that it came close to paying off all its debts for the first time in 160 years.