NEW YORK — Investors finally got what they wanted from the European Central Bank: a concrete plan to support struggling countries in the region by buying up large amounts of government bonds. That set off a global market rally and sent U.S. indexes to four-year highs.

The Standard & Poor's 500 index jumped to its highest level since January 2008, just one month into the Great Recession. European markets also surged. Treasury bond prices and the dollar dropped as traders sold low-risk investments.

The gains were extraordinarily broad; 98 percent of the stocks in the S&P 500 index rose.

"There's just a sea of green," said JJ Kinahan, TD Ameritrade's chief derivatives strategist. "It's pretty fun."

At a long-awaited meeting Thursday, Mario Draghi, the ECB's president, unveiled a new program to buy government bonds from the region's struggling countries with the aim of lowering their borrowing costs. Draghi said the program will have no set limit on how much it can buy.

Kinahan praised Draghi for two details in the plan. He didn't declare a limit for the bond-buying program and also said it wouldn't put itself first in line in the event of a default, something investors had been clamoring for. Both details should make other investors more willing to buy government bonds along with the ECB.

"In a situation where it was easy to have a slip-up, it seems like he did everything right," Kinahan said.

The S&P 500 index jumped 26 points to 1,429 shortly after noon. The Dow Jones industrial average surged 233 points to 13,281. The Nasdaq composite index jumped 62 points to 3,131.

European stock markets also jumped in response to Draghi's announcement. Germany's DAX and France's CAC-40 each soared 3 percent.

The gains were even bigger in Spain and Italy, the two largest countries to become caught up in the region's long-running government debt crisis. Spain's benchmark index soared 5 percent, Italy's 4 percent.

The interest rates on their government bonds also fell sharply. That's a sign investors anticipate a surge in demand for them as the European Central Bank starts up its bond purchase program. Spain's benchmark 10-year bond yield fell to 6 percent from 6.39 percent. Italy's comparable bond yield fell to 5.21 percent from 5.43 percent.

Traders shifted money out of U.S. Treasury bonds, considered one of the world's safest places to stash money, and the drop in demand lifted yields. The yield on the 10-year Treasury note rose to 1.67 percent, up from 1.60 percent late Wednesday.

In an encouraging sign for the U.S. job market, a report from the payroll processor ADP said businesses added 201,000 jobs last month, the most reported by the survey since March.

Separately, the Labor Department said the number of people applying for unemployment benefits fell by 12,000 last week to 365,000. That figure won't affect the August jobs report, due out Friday, but could be a sign of a better hiring this month.