How is it that everyone on earth seems to be happy shopping at Walmart? “Eight out of ten American households shop at Wal-Mart at least once a year. Worldwide, more than 100m customers visit Wal-Mart stores every week. Photographs circulated over the internet and purporting to come from the Exploration Rover show NASA’s recent discovery of a Wal-Mart on Mars. The mathematics of big numbers suggests that Wal-Mart’s growth must slow. Amazingly, the opposite appears to be happening.”