Walmart's Crime Problem

From the current issue of Bloomberg Businessweek -

• More than 200 violent crimes, including attempted kidnappings and multiple stabbings, shooting, and murders, have occurred at the nation's 4,500 Walmart's this year, or one a day.
• Walmart has one worker for every 524 square feet of retail space - a 19% increase in space per employee from a decade ago.
• Greeters have been removed from all Walmart stores.  No greeters, removing people for self-checkout, less security guards > crime per Walmart store?
• Target < crime than Walmart, but Walmart >operation hours than Target.
• Walmart decides on the security budget each store based in part on a database of how much crime happens on its property.