"When imports are sent to market, they usually stop at a fewplaces along the way, where they are switched from rail to truck orfrom larger trucks to smaller ones," Suran explains. "But exportsusually go straight from the place of manufacture to the port ofexit with no need for intermediary transfer sites. Importedconsumer goods in particular can end up at multiple warehouse orrepackaging centers before they reach their destination with storesor individual buyers."

Consequently, she says, the recent surge in exports due to thedeclining value of the dollar will not compensate for a reductionin imports due to lowered consumer sales. But while this ruleapplies to most markets, it is not necessarily true for marketswith a strong manufacturing base. "Detroit and Ann Arbor, forexample, show a reverse correlation because of the number ofproducts manufactured for export. What's important, though, is thatthese goods won't be stored or repackaged again till they getoverseas," she notes. "It appears as though all trade flows are notcreated equal, at least when it comes to warehouse demand."

In addition, the economist tells GlobeSt.com, conventionalimport and export measures also provide inadequate gauges fordetermining industrial space demand. "Most trade data is quoted indollar terms," Suran points out. "But this presents serious issuesbecause the value of a product has very little if any relation tothe amount of space required to store it. I could have a milliondollar diamond ring, but it's going to require a lot less spacethan a $20,000 automobile or $600 couch. It's the merchandise notthe cost that matters."