NEW YORK — They sold in May and went away, all right.
With a disappointing finish on Thursday, the stock market closed what was by some measures its worst month in two years. Over five dismal weeks, Facebook fizzled, a debt crisis in Europe loomed, and nobody was in the mood to buy.
When May was mercifully over, the Dow Jones industrial average and other major indexes had erased most of the strong gains they built up through March and held on to in April.
“Any time the market dips like this, it erodes some confidence,” said Craig Callahan, co-founder and president of ICON Advisers in Denver. “It scares people out of the market. All of the above, May has done that.”
The Wall Street adage holds that investors should avoid the stock market for the months of May through October, commonly known as “sell in May and go away.”
It may not be sound strategy all the time — many financial advisers say it’s foolish — but this year it looked like good advice.
The Dow lost 820 points for the month, or 6.2 percent, its worst showing since May 2010. That month, investors were spooked by a one-day “flash crash” in stocks when a large trade overwhelmed computer servers.
This May, stocks slid lower all month. The Dow closed down 26.41 points on Thursday to end the month at 12,393.45. It declined on all but five of 22 trading sessions.
The Standard & Poor’s 500 index dropped 2.99 points to close at 1,310.33. It fell 6.3 percent in May, its worst month since September. The Nasdaq composite index fell 10.02 points to 2,827.34, and had its worst month in two years.
On Thursday, investors latched on to a sliver of good news in the morning: May sales from retailers like Target and Macy’s looked healthy, and sent stock futures higher.
Then the government offered two unpleasant pieces of economic data. The number of people applying for unemployment benefits rose to a five-week high, and economic growth in the first quarter of the year was slower than first thought.
Underscoring the crisis in Europe, the head of the European Central Bank, Mario Draghi, told European leaders that the setup of the 17-country euro currency union was unsustainable “unless further steps are taken.”
The Dow was down as much as 103 points and up as much as 70 before ending slightly lower. Energy companies were the worst performers for the day and the month. The price of a barrel of oil, which ended April at almost $105, ended May at $86.53.
Worried about Europe and the weaker readings on the U.S. economy, investors continued a stampede Thursday into U.S. government bonds, which they see as a safer place to put their money.
The yield on the benchmark 10-year U.S. Treasury note tumbled to its lowest level on record, 1.54 percent. The yield rose later in the day to 1.57 percent. It was 1.62 percent on Wednesday and 2 percent in early January.
The 10-year Treasury yield was 1.55 percent in November 1945, after the end of World War II, when government price controls kept interest rates down to preserve financial stability.
In the stock market, the “sell in May” strategy posits that investors can make should sit out the summer and early fall because prices don’t rise as much and investors can make more money in other investments.
The math is compelling. From 1926 through last year, the S&P 500 rose an average 4.3 percent in the six months of May through October, versus 7.1 percent in November through April.
The problem, critics point out, is that stocks move widely above and below their averages from year to year.
One researcher, Larry Swedroe of Buckingham Asset Management, found that “sell in May” beat an ordinary strategy of buying and holding stocks if you started investing in 1960, 1970 and 2000, but not if you started in 1950, 1980 or 1990.
But this time, at least, it would have worked. Investors who bought stocks exactly according to the Dow last Nov. 1 and sold them on April 30 would have gained 13 percent. Investors who held on through May would have seen that gain cut in half.
For the calendar year, the limp May left the Dow up 1.4 percent, the S&P up 4.2 percent and the Nasdaq up 8.5 percent. Two months ago, all three indexes were up more than twice as much.
The month’s most spectacular market blunder was Facebook, which debuted on the Nasdaq exchange May 18 at $38 a share. By Thursday’s close it had fallen more than $8 from there.
The stock’s first day was complicated by technical problems at the Nasdaq, and questions later emerged about whether Morgan Stanley, which helped take the company public, had told only select clients about an analyst’s negative view of the stock.
JPMorgan Chase stock lost 23 percent of its value during the month after the bank disclosed a surprise trading loss of $2 billion or more — a black eye for CEO Jamie Dimon, who has built a reputation as a master of risk management.
Then there was Europe. Troubles in Greece dominated headlines for much of the month, but Spain has been the market’s albatross this week. It will have to spend almost $24 billion to bail out one of its biggest banks.
There is still no agreement over how to solve Europe’s debt crisis: Stronger countries like Germany want governments to cut spending, but voters in weaker countries like Greece have shown they are in no mood for more fiscal pain.
On Thursday, the European Union demanded that Spain provide more details about how it plans to finance the overhaul of its banking sector.
Spain’s key stock market index was flat, while Greece rose nearly 3 percent. Borrowing rates for Spain fell somewhat, suggesting investors were feeling a little better about that country’s finances.
“Greece is a failed chemistry experiment,” said Michael Strauss, chief investment strategist at the Commonfund investment firm in Connecticut. “But we are more worried about Spain because of its size and the scope.”
Strauss said he advised clients to take money out of stocks in early spring, when the S&P was above 1,400, or about 90 points higher than where it closed Thursday.
Strauss expects the index to return to 1,385 before the year is over, though he cautioned such a gain might not last.
May’s results are a familiar template. In both 2010 and 2011, the market rose for several months before falling in May because of concerns about debt in Europe.
Linda Duessel, market strategist at Federated Investors in Pittsburgh, argued that this May’s decline was only natural after the run-up at the beginning of the year.
“After you get a good run, you get a correction,” Duessel said. “Corrections are a very normal part of the cycle.”
Among the stocks making big moves Thursday:
— Talbots, the women’s clothing chain, rose $1.15, or almost 90 percent, to $2.44 after announcing that it will be bought by a private company, Sycamore Partners.
— TiVo, the maker of digital video recorders, fell 42 cents, or 4.7 percent, to $8.54 after posting a first-quarter loss.