Take Tuesday, when Donald Trump said American shares are giving investors “a tremendous opportunity to buy.” Reasonable people can differ on whether it mattered, it’s hardly the first time he’s mentioned stocks, and Trump gets a fair amount of blame lobbed at him for the sell-off as well. Whatever the case: he said it, and the S&P 500 shot up as much as 2.7% after four straight days of losses and the worst Christmas Eve trading session ever.

Perhaps the most famous instance of presidential stock prognostication was in March 2009, six days before the financial crisis bottom, when Barack Obama told reporters that “profit-and-earnings ratios are starting to get to the point where buying stocks is a potentially good deal.” His comments came a day after the Dow dropped below 7,000 for the first time since 1997 and the S&P 500 hit its lowest level since October 1996. Even with the recent rout, the S&P 500 is up more than 250% since March 2009.

“It is not unheard of to have presidents comment on the stock market, even though it’s not considered to be a good idea. It can actually spook investors,” said Steffen Schmidt, professor of political science at Iowa State University. For his part, Schmidt took Obama’s advice and bought stocks in 2009. “I had my 401k manager buy some best picks. They proved to be a great value,” he said, adding that he bought shares of energy stocks following Trump’s comments, as well.

Trump often talks about the market and uses it as a barometer of his success. Since his election, he’s tweeted about stocks more than 35 times.

“President Trump, unlike previous presidents, has staked much of his economic success on the stock market. It’s not crazy in that sense to encourage people to buy stocks,” said David Primo, associate professor of political science and business administration at the University of Rochester. “It’s atypical for presidents generally, but given the way the president has developed his economic platform, it’s not that unusual.”

Herein, with the help of historians, university professors and Cumberland Advisors, a sampling of market sentiment from presidents past:

Jimmy Carter

President Carter, who was in office from 1977 to 1981, “spread gloom and doom” about the energy crisis that engulfed the nation at the time, said Schmidt. The crisis saw oil prices jump roughly 350% thanks, in part, to an OPEC oil embargo.

“I think that until the question of energy is resolved, the uncertainty about this subject and the realization that our excessive imports of oil or adverse balance of trade is going to be permanent, those two things are going to contribute to the deleterious effects of increasing interest rates and also uncertainty in the stock market,” Carter said in 1978.

Ronald Reagan

In October 1987, President Reagan said soaring federal deficits helped trigger one of the largest one-day drops in Dow Jones history, when the index fell nearly 23%. Traders dubbed the day “Black Monday.”

“I couldn’t understand, at the beginning, that creating 14 million new jobs, eliminating inflation—or virtually eliminating it, bringing it down—lowering interest rates, increasing the prosperity of the people—I just wouldn’t understand that that could hurt the stock market,” he said. “I think everyone has been caught by surprise in this. And it is true that at this point of the day the market is in a far better situation than it was yesterday at this time, with about the same number of sales of stock—trading of stock. But I’m very pleased and gratified with the action that has been taken so far by the Federal Reserve Board and the fact that two of the major banks have lowered their interest rates.”

Bill Clinton

President Clinton in an October 1997 speech focused on the strength of the U.S. economy and avoided talking about the stock market during the Asian currency crisis. His comments came one day after the Dow Jones lost 554 points—the biggest ever point loss at the time—that temporarily suspended trading on U.S. stock markets.

“It may be disappointing, but I think it is neither prudent nor appropriate for any president to comment on the hour-by-hour or the day-by-day movements of the market,” the president said.

George W. Bush

President George W. Bush spoke to the nation in September 2008 as the financial crisis intensified, saying that his administration was working on addressing the root causes behind market instability.

“I’m a strong believer in free enterprise, so my natural instinct is to oppose government intervention. I believe companies that make bad decisions should be allowed to go out of business. Under normal circumstances, I would have followed this course. But these are not normal circumstances. The market is not functioning properly. There has been a widespread loss of confidence, and major sectors of America’s financial system are at risk of shutting down. The government’s top economic experts warn that, without immediate action by Congress, America could slip into a financial panic and a distressing scenario would unfold. More banks could fail, including some in your community. The stock market would drop even more, which would reduce the value of your retirement account. The value of your home could plummet. Foreclosures would rise dramatically.”