LAS VEGAS—The International Council of Shopping Centers estimates that 25 percent of the nation's retail leases are either conceived or finalized at the group's annual convention here.

The hub of activity is a giant leasing mall featuring more than 1,000 developers and retailers. Companies open extensive booths with offices for deal making, walls of pamphlets advertising available properties, and dining areas for entertaining.

But Indianapolis-based Simon Property Group Inc., the nation's largest owner of shopping malls, has been conspicuously absent for two years. Simon last year moved its leasing operations to Caesars Palace, where the company owns the top-performing mall in Las Vegas, The Forum Shops at Caesars.

The company blamed its departure on the high price for exhibit space, now $8.25 per square foot, and on the economic downturn. In 2008, Simon had the largest booth at the show at more than 26,000 square feet—the size of a small grocery store.

After that show, both Simon and Australian mall owner Westfield Shopping Centers signed two-year deals with Caesars for private conference space. The companies are planning to return for the 2011 show.

The leasing mall isn't the same without the dominant player, and the separation also makes it tough for Simon staff members to stay connected. This year's event runs from May 23-25.

"We want them back, and they want to be back, and the indication is they will be," said Jesse Tron, a spokesman for the not-for-profit ICSC.

Tron said details of the deal, including booth size, still are being finalized.

Simon spokesman Les Morris did not respond to a request for comment.

Simon's convention headquarters booth, which it first used in 2007, looks anything but temporary. The compound is surrounded by walls covered with flat-panel TVs, and the entryway is covered by a towering arch on which SIMON is spelled out in letters about as tall as a person. The luxurious digs include a restaurant, dozens of offices, boardrooms and multimedia displays.

The reunification is a good omen for the retail market, said Nick Wright, a principal in Indianapolis-based Newbridge Commercial Real Estate.

"Assuming the location and size of the booth are the same and all Simon leasing agents start attending again, it could be a great sign for a more active ICSC than we've seen in recent years," Wright said. "It's also a sign Simon may be forecasting a brighter overall retail economy in 2011 as more retailers and restaurants aim for expansion."

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