Cities both large and small are boosting the size of their convention centers in hopes of attracting free-spending conventioneers. But in a provocative new study, the Washington-based Brookings Institution (www.brookings.edu) says the race to build bigger and bigger convention centers may have no payoff, as the overall convention marketplace in the United States languishes at 1993 attendance levels.

Author Heywood Sanders blames overly optimistic attendance predictions with prompting convention center expansion. Over the past decade, public spending on convention centers has doubled to $2.4 billion annually, Sanders says, increasing convention space by more than 50 percent since 1990. Nationwide, 44 new or expanded convention centers are now in planning or construction.

However, the disruptions of 9/11 (which made travel a greater headache), consolidation in certain major industries, and ongoing advances in communications technology are eroding the growth of shows themselves, the Brookings study says.

The rush to expand convention centers plagues cities of every stripe, the study maintains. Not only are second- and third-tier cities hoping to snag convention business, but big-capacity cities such as Chicago, New York and Atlanta are in the game, as are cities with strong tourist draws, such as San Francisco and Boston.

However, even emerging powerhouse convention towns such as Las Vegas and Orlando, Fla., which have grabbed convention business from the long-standing convention capitals, are booking only break-even business in their newly expanded convention facilities.