Check out this
post from Freakonomics Blog:

** There’s an interesting news
brief in today’s N.Y. Times about a report just
issued by the Food Marketing
Institute about shoplifting in supermarkets. In previous years,
health and beauty products were the most frequently shoplifted items,
making up 23% of all stolen items in 2000. [snip…]

“The report also suggested,” Mindlin writes, “that self-service
checkout lanes, where customers scan and pay for their purchases
themselves, are surprisingly theft-free. Of the roughly 5,400 stores
in the survey with self-checkout lanes, 63.6 percent reported no
increase in theft rates.”

(Read the whole thing**! Stealing
in Supermarkets)