WASHINGTON — In a fascinating recent talk, White House chief economist Jason Furman took a crack at solving a great puzzle of the lackluster recovery: weak business investment.

The explanation takes on added urgency after the latest disappointing job report. Although September’s unemployment rate remained at 5.1 percent, the number of new payroll jobs was only 142,000, much less than expected. Vigorous investment spending is the missing piece in a strong recovery.

Of course, businesses haven’t stopped investing entirely. In 2014, they spent $2.2 trillion on buildings, equipment, software and research.

For many large firms, the amounts are huge, says economist Michael Mandel of the Progressive Policy Institute, a left-leaning think tank. In 2014, AT&T led in business investment at $21.2 billion, followed by Verizon at $16 billion and Exxon Mobil at $12.4 billion.

But the spending represents a reduction from what — based on past trends — might have been expected. By Furman’s calculations, annual business investment is running roughly $400 billion short of where history suggests it should be. Furman put the gap at 2.3 percent of gross domestic product. With GDP near $18 trillion, that’s about $400 billion.

Stronger investment would almost certainly mean more jobs and, possibly, higher wages. Just as important, investment in new equipment and new technologies boosts productivity, which is essential for higher living standards. Weak investment implies weak gains in living standards. Consistent with this, annual labor productivity growth has averaged only 0.4 percent from 2011 to 2014. That’s way below the post-World War II average of about 2 percent.

So what’s hampering business investment?

One theory is that Obama administration policies like the Affordable Care Act have discouraged it by fanning uncertainty and fueling an anti-business climate. This seems questionable, because the investment shortfall afflicts most advanced economies. Compared to projections before the 2008-09 financial crisis, business investment is down 16 percent in the United States, 15 percent in the United Kingdom, 20 percent in Japan and 11 percent in eurozone countries, Furman reported.

Whatever the defects of Obama’s policies, it’s hard to blame them for a global investment slump. Indeed, Furman noted, business profits have been strong in recent years. But rather than invest, companies have channeled much of the cash flow to shareholders through higher dividends and stock buybacks.

Another theory is that the economy has experienced a “structural” shift: Tech companies like Facebook require less investment than their heavy-industry predecessors like U.S. Steel.

Furman is skeptical. True, the investment needs of many tech firms are modest. But consumers use these tech applications “through the often large investment in wired and wireless networks made by Internet service providers.” AT&T’s and Verizon’s massive capital spending attests to this.

What ultimately explains the investment slowdown, Furman contends, is the slow-growing economy. In many industries, capacity is ample to satisfy moderate demand. If the economy were growing faster, Furman says, companies would invest more. Not surprisingly, this explanation supports the White House’s proposal to increase the economy’s growth by lifting the existing caps on federal spending.

This may be true, but the argument is also circular: A stronger economy would boost investment; but one reason the economy is weak is that investment is weak. The crucial question is this: Why has investment deviated so markedly from its postwar trends, even in the face of impressive profits? The answer may be something that Furman barely considers: the legacy of the financial crisis and Great Recession.

Arguably, it changed business behavior, because companies were surprised by its occurrence and severity. Since then, they have become more cautious and risk-averse. They only approve projects that, compared with the pre-crisis years, have higher rates of return and less uncertainty.

That’s consistent with strong profits despite a weak recovery. It also helps explain why the investment slump is global — after all, the financial crisis and Great Recession were global. And it helps explain why the investment slump has been so hard to cure: Its origins lie in changed attitudes, which are hard to reverse.

Robert Samuelson is a columnist with the Washington Post Writers Group.