Few of us realize how much the cost of that item we just purchased at some retail outlet was driven up by criminals, but it is substantial, and growing.

Theft cost American retailers nearly $42 billion last year, says a study by the National Retail Federation and the University of Florida. The study found that the shrinkage rate as a percentage of total sales rose slightly to 1.61 percent of sales in 2006. It had been 1.6 percent in 2005. So we can assume that the prices of things we buy are hiked at least 2 percent because of shoplifting, burglaries and, most disgusting, employees helping themselves to goods they do not pay for.

One of the most sobering reports on the subject comes from Marcus Kabel, Associated Press business writer, in a recent story about theft, or shrinkage, problems of Wal-Mart, the world’s largest retailer. Inventory losses for Wal-Mart this year are due to rise to more than $3 billion due to shoplifting, employee theft, paperwork errors and supplier fraud. Wal-Mart generated sales of $384.6 billion last year.

Retail consultant Burt Flickinger III, along with other analysts, contend that the increase in theft may be tied to Wal-Mart’s decision last year to no longer prosecute minor cases of shoplifting so they could focus more sharply on organized shoplifting rings. Former employees say that staffing levels including security personnel have been reduced and that it is easier for crooks to profit.

All this is far from new phenomenon, of course. Wal-Mart founder Sam Walton often said that theft is any retailer’s top profit-killer. The company for a long time neglected to address the “shrinkage” problem publicly. But securities regulations for publicly held companies such as Wal-Mart now require companies to alert shareholders to significant developments that could affect their holdings. Certainly a $3 billion-plus theft loss is “significant.”

In some sectors, shrinkage has been declining since the mid-1990s as retailers have been investing in closed circuit television and other new technology. Yet here is the most depressing statistic: About 47 percent of the shrinkage dollars in retailing result from employee theft.

While it is substantial, only about 32 percent is a result of shoplifting, which most would figure is the costliest category. Administrative efforts account for 14 percent while supplier fraud accounts for 4 percent. The remaining 3 percent of shrinkage is unaccounted for.

So there are thieves among us and some of them are akin to foxes in the henhouse – employees who choose to rip off employers such as Wal-Mart. Next time you make a retail purchase, check the price and consider the extra 2 percent, a hidden sales tax, that is involved.

The illegal behavior costs us all.