Walmart, the world's largest retailer and the largest company in America based on sales and employees, has tried to argue since the beginning of the recession that it can revive its moribund sales growth in the United States. The odds that it can accomplish this are extraordinarily low. In the quarter which ended on April 29, same-store sales in the US fell 1.1 percent and revenue was up only 0.6 percent to $62.7 billion. The company's growth is constrained by the fact that six of every ten dollars of Walmart's sales come from the U.S. Slow growth there has been a source of concern. Bill Simon replaced Eduardo Castro-Wright as head of U.S. operations in June 2010. Simon said his main focus would be on increasing store traffic and same-store sales while keeping prices low. That's been easier said than done as economic growth slowed and gas prices soared.