NEW YORK (AP) — Retail sales for the four-day holiday weekend, starting with Thanksgiving Day, rose 8.7 percent from a year earlier, a key data service said Thursday.

The figures from MasterCard Advisors' SpendingPulse show the holiday shopping season got off to a robust start with help from midnight openings Thanksgiving evening and deep discounting.

Retailers count on the holiday shopping season, which includes November and December, for as much as 40 percent of their annual sales.

Retail sales totaled $50.06 billion for the four days, excluding autos but including gasoline, food and online purchases. SpendingPulse tracks payments in all forms including cash.

For the four weeks from Oct. 30 through Saturday, Nov. 26, SpendingPulse's holiday index, which includes spending on clothing, general merchandise, toys and electronics and in department stores, rose 4.7 percent to $125 billion, compared with a 2.6 percent increase last year.

"The holiday season is off to a good start," said Michael McNamara, vice president of research and analysis for MasterCard Advisors' SpendingPulse. "But we have to see how it holds up. A lot of the season is still in front of us."

The data follows other reports that also point to a big surge in spending over the weekend.

A survey by the National Retail Federation found Americans spent $52.4 billion over the four-day Thanksgiving weekend, the most ever recorded. The average shopper spent $398.62, also a record, up from $365.34 a year ago, the NRF said.

ShopperTrak, a Chicago-based research firm that watches sales and traffic at 25,000 stores, said sales the day after Thanksgiving rose 6.6 percent to $11.4 billion, the largest amount ever spent on what's known as Black Friday.

And the research firm comScore Inc. said sales on Cyber Monday, the first business day after the Thanksgiving weekend, rose 22 percent from 2010 to $1.25 billion, producing the biggest day ever for online sales.

When major chain stores including Target Corp. and Macy's Inc. report their November sales comparisons on Thursday, which will add still more detail. Those figures, for revenue at stores open at least a year, are a key indicator of retailers' financial health.