NEW YORK (AP) -- Despite being known as the stock market’s jinx month, this October is shaping up to be one of the best months on record. The main reason is progress in Europe toward containing that region’s debt crisis.

The Standard & Poor’s 500 index has gained 12 percent for the month, which puts the broadest stock-market measure on track for its best month since January 1987. Even after a decline Monday, the Dow Jones industrial average is still up 10.6 percent in October, its best month since August 1982.

The big breakthrough in Europe came early Thursday of last week, when European leaders reached a far-ranging agreement aimed at shoring up the region’s banks and preventing a debt crunch in Greece from bringing down Europe’s financial system.

But a lack of many key details in the plan has made markets jittery again, and on Monday fresh reminders of how the Europe crisis can affect U.S. financial institutions helped bring the market lower.

Bank stocks fell broadly Monday after the securities firm MF Global filed for bankruptcy protection. Last week the company’s debt was downgraded to junk status by ratings agencies concerned about its large holdings of European government debt. The company is headed by former New Jersey Governor and Goldman Sachs chairman Jon Corzine.

MF Global’s bankruptcy filing labeled JPMorgan Chase & Co. the brokerage’s largest creditor. JPMorgan, widely considered the strongest of the big banks, dropped 3.4 percent.

Other banks sank. Bank of America lost 4.3 percent. Citigroup dropped 5 percent, and Morgan Stanley 5.8 percent.

The Dow was down 153 points, or 1.3 percent, to 12,076 at 2:24 p.m. ET. The drop comes after the Dow closed out its fifth straight week of gains, its best winning streak since January.

The Standard & Poor’s 500 index was down 17, or 1.3 percent, to 1,268. Energy and materials companies led the decline. The Nasdaq composite is down 28, or 1 percent, to 2,709.

The Organization for Economic Cooperation and Development warned Monday that European economies will see a “marked slowdown” next year. The organization called on the European Union to provide more information on how it plans to stem the debt crisis.

Major stock indexes dropped in Europe. Germany’s DAX fell 3.2 percent. France’s CAC-40 dropped 3.2 percent. Both still closed the month with strong gains. The German index rose 11.6 percent, the French one 8.7 percent.

October has earned a reputation as a famously bad month for stocks. The October 1929 crash divided the roaring 1920s from the Great Depression of the 1930s. It’s the month that has given the market two black eyes: Black Tuesday in 1929 and Black Monday in 1987.

This October started off on a sour note when the Dow and S&P 500 hit their lowest point for the year Oct. 3, but the market has soared since then. The Dow is up 13.3 percent since then, the S&P 15.2 percent.

Investors were relieved when European leaders made progress in tackling the region’s debt crisis in recent weeks. Worries that the U.S. might slip into a recession have faded, and many big U.S. companies like McDonald’s Corp. have reported stronger profits for the third quarter. More than three-quarters of U.S. companies in the S&P 500 that have reported results so far had earnings that beat analysts’ expectations, according to the financial data provider FactSet.

“It’s a rally off what was a very pessimistic view of the global economy,” said Todd Henry, an emerging-market equity specialist at T. Rowe Price. “Does it have legs? I think that’s yet to be seen.”

The European debt crisis is still far from fixed. One troubling sign is that borrowing costs for Italy and Spain have increased, a signal that traders remain worried about their ability to pay their debts.

© 2011 The Associated Press