Now that it has finally happened, don’t expect the Federal Reserve’s long-awaited rate cut to make all that much of a difference for the economy.

In the weeks leading up to Wednesday’s decision to cut the benchmark Fed funds rate by 0.25 points to 2.25 percent, the stock market seemed to leap whenever Jerome H. Powell, the Federal Reserve chair, hinted that a cut was coming.

On Wednesday, apparently disappointed by the modest size of the first rate cut since 2008, the stock market fell: The S&P 500 declined 1.1 percent.

President Trump certainly wanted the Fed to take action. He said so numerous times on Twitter and on Tuesday morning demanded “a large cut”— larger, presumably, than the Fed delivered.

More rate cuts may be coming. Yet a rather important problem is lurking for anyone relying on Fed cuts to accomplish something substantial, like preventing a slowdown or even staving off a recession.

It’s not just that the Fed has a “short runway” — that rates are already so low that it is impossible to cut them four or five percentage points in the face of a recession, as the Fed has done in the past. The real problem is that recent experience and new economic research suggest that rate cuts in general may have a more modest impact on the economy now than they usually do.

You can understand Mr. Trump’s concern about the economy. It has been the one bright spot in his approval ratings, and now it seems to be slowing.

Under President Barack Obama, growth of the gross domestic product averaged about 2.2 percent after the recession ended in 2009. Under Mr. Trump, with an assist from a large, deficit-financed tax cut, G.D.P. ticked up.

But with that stimulus mostly behind us, G.D.P. growth has slowed. The latest data shows it fell back to 2.1 percent in the three months through June, and the forecasts for the current quarter are even lower. Beyond the United States, the International Monetary Fund has downgraded its forecast for world economic growth yet again.

The worry, arising from some important new research, is that the benefits of Fed rate cuts in today’s environment may be substantially overrated.

Typically, when rates drop, consumers buy more durable goods like washing machines and cars, homeowners refinance their mortgages and eff ectively get a tax cut, and businesses invest more because the cost of borrowing goes down. But lower rates may have much less impact on these behaviors now. In the language of economics, the economy is suffering from a “weakened monetary transmission mechanism.”

Take spending on consumer durables. A recent study by economists at the Federal Reserve Bank of Minneapolis and the University of California, San Diego, notes that these purchases occur in lumpy spurts. People tend to spend nothing on such items for long periods, then spend a lot all at once, when money is cheap and prices are enticing.

The problem now is that once-in-a-lifetime offers don’t generate the same excitement if they are repeated every week. And, the study suggests, after 10 years of extremely low interest rates, there probably aren’t many consumers with pent-up demand, waiting for rates to fall. Because so many people have already made their big purchases, the economic kick from a rate cut is smaller than it would be at a “normal” time.

Economists at Northwestern, Copenhagen University and the University of Chicago’s Booth School of Business have shown the same thing about mortgages. Because most mortgages have fixed rates, a Fed rate cut will affect these homeowners only if they refinance.

Typically there’s a large group of people with a pent-up demand for a cheaper mortgage, and once they get one, the benefit is roughly equivalent to receiving a big tax cut: They have a lot more money to spend on other things. But if rates have already been low for a long time, most of those people will have already refinanced along the way. A cut in rates will not deliver the same punch it usually would.

A similar dynamic probably helps explain why the 2017 corporate tax cut has had such an underwhelming impact on companies’ capital investment. Fundamentally, there wasn’t much pent-up demand for investment after years of low rates, accelerated depreciation, “temporary” investment expensing and other stimulus. That lack of pent-up demand also means that cutting interest rates now is unlikely to entice businesses to invest much more.

So it’s a twofold problem: The Fed has less room to cut rates, and the benefit from cutting them is smaller than usual. We should be wary of vesting too much importance on Fed moves.

In a world of weakened monetary policy, some might view the recent federal budget deal as a major fiscal boost. But it’s worth remembering that the budget compromise increases spending only compared with long-since-abandoned limits set back in 2011.

Compared with last year (which is what matters for G.D.P. growth), federal spending is essentially just growing with inflation. And with the deficit already at troublingly highly levels for an economy not fighting a major war or recession, it’s not clear there would be space for new fiscal stimulus at all.

The good news is that consumers remain confident, unemployment is low, and growth of 2 percent is a lot better than a recession. The bad news is that if it things worsen, there might not be a whole lot out there to save us.

Austan Goolsbee, a professor of economics at the University of Chicago’s Booth School of Business, was an adviser to President Barack Obama. Follow Austan Goolsbee on Twitter: @austan_goolsbee