San Francisco ? While many Americans sleep off the effects of oversize turkey dinners, Glenn Murphy will mingle with holiday hordes at an outlet mall.

Murphy, chairman and CEO of The Gap Inc., said he and other executives are assessing whether the retail industry’s “doorbuster” promotions – which begin at midnight, only hours after the pumpkin pie is served – are worth the additional costs and scheduling hassles.

Besides midnight openings at 170 Gap Outlets nationwide, about 90 percent of the company’s Old Navy franchises will open at 5 a.m. today, traditionally among the busiest shopping days of the year. That’s two hours earlier than Old Navy opened last year.

“There is a point from an industry perspective where you get diminishing returns,” said Murphy, who is spearheading an ambitious turnaround and aggressive cost-cutting campaign at the San Francisco-based retailer. “You can bet a number of people at Old Navy will be going through the numbers, doing a careful economic analysis.”

Gap is one of dozens of retailers opening earlier and offering special deals during pre-dawn hours on Black Friday – named because it was traditionally when stores became profitable. Sales registered on the day after Thanksgiving are considered an important indicator of the nation’s economic confidence.

Toy chain KB Toys Inc. will have 135 stores open at midnight, 30 percent more stores than last year. J.C. Penney Co. stores will open at 4 a.m. today, an hour earlier than last year.

Mervyns will also open at 4 a.m., while Circuit City Stores Inc. and Best Buy Co. will open at 5 a.m., and Target Corp. will open at 6 a.m.

Most of Wal-Mart Stores Inc.’s locations will open at 5 a.m. For the first time, the world’s largest retailer has moved many Black Friday promotions to Thursday. The company, which published details of its “secret” holiday deals in a news release Monday, aims to “to catch early bird shoppers as the turkey hits the table.”

Given the relatively low cost of retail labor, doorbusters are no-brainers, said Stifel Nicolaus & Co. retail analyst Richard Jaffe.

“It’s a simple math problem: You pay rent 24 hours a day. You own the merchandise,” Jaffe said. “The incremental cost of staying open is two sales people at $12 an hour, plus electricity. You sell two sweaters and you’ve broken even.”

Doorbusters also get priceless free publicity from news organizations that chronicle Black Friday, typically a slow news day.

“You can’t discount the sizzle factor,” Jaffe said.