From wire and staff reports

Wal-Mart Stores Inc. charged the wrong price to shoppers in California and the Midwest at a rate that exceeds those set by federal guidelines, according to two union-commissioned university studies released Monday.

Attorneys general in Illinois and California said the reports raised serious concerns.

A spokesman for the Maine attorney general’s office said Tuesday that it had been asked to join the investigation. “We’ll consider it,” said Charles Dow, the spokesman. He said the office hadn’t received any complaints of problems with scanned prices at Wal-Marts in Maine “that I know of.”

The two studies said random purchases at 60 Wal-Mart stores in California found that the wrong price came up 8.3 percent of the time. At 78 stores in Illinois, Indiana and Michigan, checkout scanners rang up the wrong price 6.4 percent of the time. In both states, some prices were higher and some were lower.

The National Institute for Standards and Technology says that for every 100 items scanned, no more than two should have the wrong price. The NIST’s last industry-wide study, in 1998, found the rate at 3.35 per 100.

The recent studies were commissioned by the United Food and Commercial Workers, which has been unsuccessful in its attempts to organize Wal-Mart workers for years, and released by a UFCW-backed campaign group, Wake Up Wal-Mart. The research was conducted by the University of Illinois-Chicago Center for Urban Economic Development and the University of California-Berkeley.

“A majority of Wal-Mart stores tested in this evaluation of price accuracy demonstrated errors in pricing that exceeded federally accepted standards for large retail establishments,” the California and Midwest studies concluded.

The researchers said the average cost of overcharges was more than that of undercharges.

Wal-Mart said its last internal audit found an error rate of 2.4 percent – less than the 1998 national study by NIST – and slammed the union studies as incomplete and outdated. The company noted that the studies’ authors say their results are specific to those states and cannot be generalized for the entire country.

“This desperate attack has more holes than a pasta strainer. This is another paid attack by union critics,” Wal-Mart spokeswoman Sarah Clark said.

The California study was finished in May 2005 and the Midwest study in September 2004, with purchases made over a number of weeks before those dates. The researchers said they used NIST-developed guidelines to pick random items in nine departments, including home fashions, housewares, groceries and sales racks.

Accounting for the union-backed studies’ margins of error, 81 percent to 92 percent of the California stores had more than two errors per 100 items scanned, and between 75 percent and 94 percent of the Midwest stores had more than two errors per 100 items scanned.

There were more overcharges in California but more undercharges in the Midwest.