Salt Lake County auditors believe the local economy has been helped far less by the convention and visitors bureau than its officials claim.

In a report released Monday, auditors said they calculated the bureau generated 36 percent less money in 1989 than its officials claimed, and 37 percent less than claimed for 1990. The difference amounts to $3.9 million in 1989 and $12.5 million in 1990.But Convention and Visitors Bureau Director Richard E. Davis said several methods can be used to calculate how much money convention delegates and their spouses spend each year. He defended the bureau's figures, which were generated by a national accounting firm.

"We believe our calculations are accurate and defensible," he said in a written response to the audit.

However, Davis promised to hire an accounting firm or research organization to independently calculate expenditures by local convention delegates "so that reliable and valid data is used for reports of economic impact."

The audit said the errors were due to a miscalculation of the money spent by spouses and others who accompany delegates to conventions, and of the number of people who stay in rooms vs. the number who reserve rooms and don't show.

Salt Lake County commissioners decided not to hear the report Monday, saying they had not yet read it and were not prepared to respond.

Commission Chairman Jim Bradley said the auditors' findings demand scrutiny. "Auditors can be wrong," he said.

The commission strongly supports efforts to expand the Salt Palace Convention Center. Expansion proponents often support their arguments with figures showing how much conventions add to the local economy.

In his written response, Davis said the bureau will follow the recommendations of the audit. He said the bureau will calculate its performance using the number of people who actually pay for their rooms in addition to those who only reserve rooms. In 1989, 22 percent of the people who reserved rooms never used them, the audit said.

Auditors said they would have likedto compare the local convention and visitors bureau with other similar-sized bureaus. But the International Association of Convention and Visitor Bureaus refused to provide such information, the report said.

Davis said an international bureau consultant team, which recently studied the local facility, said "meaningful standards of comparison of bureau performance from city to city do not exist."

The Salt Lake Convention and Visitors Bureau is a private, non-profit corporation created in 1984 when county officials decided to privatize its convention promotions.