Wal-Mart almost gets it. This article: http://money.cnn.com/2011/04/27/news/companies/walmart_ceo_consumers_under_pressure/index.htm reports that Wal-Mart is worried because their customers seem to be running out of money earlier in the month than they used. Wal-Mart attributes that primarily to high gasoline prices. I'm sure that higher gasoline prices as well as higher food prices have had an effect on what shoppers spend at Wal-Mart.
Later on the report says that Wal-Mart has had seven straight quarters of sales declines. They attribute that to their prices not being low enough. Perhaps their prices are not as competitive as they once were. I think that some of their sales decline can be attributed to the economy.
But I wonder if some of the sales decline is not Wal-Mart's own doing. As with most retailers, it's hard to find a product they sell that's made in the United States. It seems to me that as more and more manufacturing jobs are lost in the United States there will be fewer people in the United States able to buy the products made overseas and sold at Wal-Mart. Wal-Mart is shrinking its own market.