These charts are signaling recession

No one knows how long the current economic expansion will continue.

But some seven years after the last recession ended, economists are keeping an eagle eye on the latest data looking for signs that another downturn may be approaching.

For now, much of the economic data is pointing to continued, if somewhat weak, growth. Companies are hiring, wages are rising slowly and consumers are spending.

But belt-tightening by businesses on investment in new equipment and buildings could be a sign of a deeper slowdown ahead, according to economists at Credit Suisse.

"Extended periods of falling real business investment are strongly associated with US recessions," they wrote in a note to clients. "That's why the recent three consecutive quarters of contraction are concerning."

In fact, the last time business investment contracted over a prolonged period, without a recession following soon, was in 1986-87. That investment pullback also followed a sharp drop in oil prices, much like the recent collapse in spending and investment on oil and gas drilling.

But cuts in business spending and investment have spread beyond the oil patch, the Credit Suisse economists noted. In the past few quarters, investment in agricultural machinery has fallen hard.

Investment in transportation equipment has also stalled, after a big run-up tied to the rapid growth of oil and gas exploration and drilling that preceded the crash in oil prices in 2014.

With pipeline capacity constrained, much of the new production of oil and natural gas had to be shipped by rail or trucks. But the bust in the oil patch has brought a pullback in transportation investment.

Some of the slowdown may be tied to general uncertainty about the election cycle, which has prompted many businesses to take a wait-and-see attitude before committing dollars to new equipment or breaking ground on new buildings.

In June, a survey of business economists found that some 60 percent said that uncertainty about the November vote is damaging prospects for growth this year.

"Businesses are generally prepared to not have everything go their way, but they have a much harder time when they don't know what's going to happen or what to expect," said Greg Daco, head of U.S. macroeconomics at Oxford Economics.

"The outlook is so muddled by political and global factors that it is hard to expect a major recovery" in business investment this year, the Credit Suisse economists said.

Still, they note that the risks to that forecast "are to the upside," largely because business investment could stage a rebound once the uncertainty of the election is over.