Wal-Mart, which draws nearly 10 percent of all nonautomotive spending in the U.S., is operating in a more difficult environment since the recession on all fronts. Dollar stores, which have expanded their assortments, are blanketing the country, and Amazon.com's vast selection and low prices are stealing Wal-Mart's key advantages.

Meanwhile, rising gas prices and other household costs are squeezing shoppers' budgets and making it tougher to stretch their remaining dollars to the next payday. A still stubbornly high unemployment rate has also hurt its core shoppers. But Wal-Mart's strategy of going back to its roots of "everyday low prices," instead of resorting to slashing prices on select items, has helped to rebuild its reputation as a low price leader and bolster its namesake U.S business. Its U.S Walmart division accounts for 62 percent of total sales.

In the third quarter of last year, Wal-Mart reversed nine straight quarters of sales declines at stores open at least a year in its namesake U.S. business. That's an indicator of a retailer's health because it excludes results from stores recently opened or closed. In the fourth quarter, Wal-Mart continued the trend. Still, there's a lot more room for improvement. For the year, the measure rose 0.9 percent compared with a 1.1 percent dip in the previous year.

Overall, Wal-Mart posted a 5.9 percent increase in total sales to $418.95 billion for the year. That excluded income from membership fees to Sam's Club, its warehouse club division. Total sales rose 1.5 percent for the Walmart U.S. division in the latest fiscal year. Net income slipped 4.2 percent to $15.69 billion. The Bentonville, Ark., company posted operating income of $26.5 billion, up 4 percent from the year before.

For its performance-based stock plans, Wal-Mart uses return on investment and total sales performance as yardsticks to determine executives' compensation.

Wal-Mart lowered the threshold for return on investment, which accounted for 26.8 percent of Duke's overall compensation, to 18.4 percent in its latest year from 18.66 percent in the previous year. The company's actual return was 18.63 percent. Gregg Rossiter, a Wal-Mart spokesman, noted that the goals for the performance-based plans are set in March.

"They're based on the operating plans to reach the company's strategic goals and are reviewed by the board, which considers economic conditions in retail and in the markets where we compete," he said.

The company announced a year ago that it would replace revenue at stores open at least a year with total sales as a yardstick for measuring performance.

Wal-Mart faces plenty of challenges. Reclaiming its reputation as the lowest-price leader is critical for Wal-Mart to sustain the upward sales trend. In fact, an increasing number of shoppers, armed with smartphones, are using big stores like Wal-Mart to browse and then checking competitors' prices while still standing in the store. They'll walk out if they get a better deal elsewhere.