As Hillary Clinton had what most polls found to be a convincing victory over Donald Trump in the first presidential debate, financial markets cheered in the same way they might respond to a particularly good piece of economic news.
During the debate, and in the hours afterward, financial instruments that bet on the future performance of US stocks rose, and ones betting on future market volatility fell. Oil prices jumped up — as they do when traders expect stronger economic growth in the future — and gold prices went down.
The moves were notable in large part because markets were cheering a Democrat, according to a new paper by economists Justin Wolfers and Eric Zitzewitz.
"In almost every case back to 1880, equity markets have risen on the news that Republicans win elections and fallen when Democrats win," the pair wrote. "The 'Trump discount' is an historic anomaly," they later conclude.
In fact, judging by trades made as Clinton enjoyed her win, "market participants believe that the S&P 500 will be worth 12% more under a President Clinton than Trump," they wrote.
It wasn't just in the US where Clinton's debate win was celebrated in real time.
British stock prices increased, and the value of the Mexican peso rose against the US dollar. Outside of Mexico, the countries whose markets and currencies were most affected tended to be ones with substantial US trade agreements.
South Korea's stock market rose "about twice as much" as markets in the US, UK, and other Asian countries, while the currencies of Canada, New Zealand, Australia, and South Korea jumped up as well.
The global breadth of market responses suggests that in the eyes of investors, a Trump presidency "is not seen as uniquely harmful to the United States, but rather is a broad global threat that impacts each of the equity markets we have studied."
The jump in S&P 500 futures on the Sunday night of the debate was small in absolute terms — they rose .71% — but the authors say that relative to how much they normally move, it was substantial. Those futures contracts have only risen by more than that on 1.2% of all Mondays from 2010 through September 2016.
Sunday nights are "traditionally a tranquil period for financial markets," the authors say. "It's is very rare for the market to move as much as it did during the debate."
There was a similarly unusual move in the days following the release of the infamous Access Hollywood tape. Gamblers on prediction markets bet Trump's chance of winning the election had fallen by 8 percentage points. In the same time period, the peso jumped up, and on that Sunday night, S&P 500 futures rose.
Traders showing preference for a Clinton win are going against the historical grain. In past elections, there has been what the authors call a "Republican premium" in stocks, which they attribute "in part or full" to the party's preference to reducing taxes.
During the 2012 election, when Mitt Romney had what was generally seen as a convincing win in the first debate, markets rallied. "In 2012, the market rose in response to an increased chance of a Republican president, which stands in stark contrast to 2016" the authors say.
All that comes "despite the fact that Trump is promising massive cuts in capital taxation," Wolfers told BuzzFeed News. If those cuts were to happen, it would be enough, "to goose the S&P." But investors aren't putting their money on it.