U.S. investors on Thursday acted as if British voters were choosing to stay in the European Union, sending stocks hurtling upward by 230 points to more than 18,000 on Dow Jones.
But by late evening, as votes were being tabulated and released overnight, voters showed they had a different idea, raising the likelihood of a rocky ride for markets on Friday.
Despite early returns showing the "remain" camp leading by the narrowest of margins, the "leave" camp has taken and held the lead throughout the night.
Final results
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Leave – 17,410,742 (51.9%)
Remain – 16,141,241 (48.1%)
All districts reporting
In a story that has since been removed, the London Telegraph reported a leading British pollster saying an exit from the EU was the most likely outcome.
On Thursday, USA Today said investors were "anxiously awaiting the outcome of the vote as analysts predict a vote to leave the EU would send global stocks tumbling due to the economic uncertainty a U.K. exit would create."
CNN warned that it is entirely possible that the American economy could take a hit, just as jobs creation is stagnates under President Obama's policies even as official unemployment rates remain low. That's mostly because of the tens of millions of people who simply have stopped looking for work and therefore no longer are counted as "unemployed."
CNN said that while the International Monetary Fund released a report that found "leaving the EU would primarily hurt the U.K. economy, it could affect the U.S., too – particularly if there's a significant negative market reaction."
The report cited Federal Reserve chairwoman Janet Yellen's comment that the vote "could have consequences for economic and financial conditions in global financial markets."
"If it does so, it could have consequences in turn for the U.S. economic outlook." she said.
Yellen said the Federal Reserve already had decided not to raise interest rates at its most recent meeting because of the threat of an economic freefall.
USA Today said it appeared investors on Thursday were betting the vote will be to stay, resulting in greater stability.
Said the report: "The Dow Jones industrial average ended up about 230 points, or 1.3 percent, with the Standard & Poor's 500 index posting the same percentage gain. The Nasdaq composite jumped 1.6 percent."
Benchmarks across Europe were similar, the report said.
Marketwatch cited Key Private Bank strategist Bruce McCain forecasting that voters "almost always favor the devil we know to the devil we don't know" and a resulting victory for the stay in side.
And Randy Frederick of Schwab Center for Financial Research said in the report, "A relief rally could ensue in the coming weeks, but substantial upside is likely to be limited by the same factors that have been weighing on the markets."
Voters headed to polls on Thursday across the U.K., but few exit polls are conducted there, so it will be actual results that reveal the decision.
The results are expected to be announced from dozens of polling districts overnight, with final totals expected overnight about 2 a.m. or 3 a.m. in New York.
In an April visit to the U.K., President Obama told Britons they should vote to stay.
"The United States wants a strong United Kingdom as a partner. And the United Kingdom is at its best when it's helping to lead a strong Europe," he said.
Obama said if the vote is to leave, American efforts will continue to focus on a trade deal with the EU, and Britain then would drop to the back of the line. He said a deal is "not going to happen anytime soon," assuming a vote to leave.
However, State Department spokesman John Kirby tempered those comments, with, "We don't anticipate anything changing the special relationship that we have with the U.K."
Zerohedge explained the votes are being totaled in 382 counting areas, with results being released overnight into Friday morning.
Campaigners on both sides said in the report that the turnout is expected to have an impact, with the lower the turnout, the more likely the "leave" vote would win.
The announced results, the report said, probably will be final, because the rules "do not provide for a national recount under any circumstances."
Local officials would decide if their results would be subject to another count.