The National Retail Security Survey found that total retail losses increased from $37.5 billion in 2005 to $41.6 billion in 2006 as overall retail sales rose.

However, despite the mounting dollar losses, the percentage of sales lost to activities such as organized crime and employee theft remained flat with last year, and totaled about 1.61% of retail sales.

"The fact that we haven't brought the number down is concerning because frankly we've invested a lot of resources in this and we've got law enforcement really active," said Joe LaRocca, NRF's VP of loss prevention.

The NRF said one big culprit behind the losses is organized retail crime, which happens when groups of shoplifters steal vast quantities of goods and typically resell them on Web sites, at flea markets or in other stores.