The 20-stock index contains such ubiquitous names as FedEx, whose earnings are usually considered a key read on economic activity, through a swath of airlines, including Southwest and Delta, to some more obscure names like rail and marine fleet operator GATX.
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Many analysts would be hard-pressed to give a good accounting of the names in the transport index, though it often is cited in discussions of whether the index is "confirming" a move higher in the much more closely followed industrials.
"It's a surprisingly good sampling of who moves stuff around the United States and what it takes to move stuff around the United States and around the world," Blitzer said.
What moves the index, though, isn't always so easy to tie to the broader economy.
Airline stocks have led the surge higher for the transports, which as an index had gained more than 10 percent by the second week of August.
Southwest had posted a 52 percent gain, Delta was up 33 percent, and JetBlue rocketed 38 percent higher amid a buying fervor that seemed to have little to do with bigger growth trends. Those gains trumped weak performances by FedEx and rail freight firm Kansas City Southern—both companies that would seem to be more in tune with economic growth.
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Abigail Doolittle, who studies technical trends at Peak Theories Research, has been watching the transports and industrials diverge sharply over the past two years, and it's a move that has left her befuddled.
"The move in the transports is more shocking to me than any of the other global indices," she said. "It's the first time I've ever thought of market manipulation. I used to look at the transports first. Now it's kind of an afterthought. They have lost that sort of edge for me."
Investors looking for the transports as guides to market movement should go elsewhere, Doolittle added.
"Transports as a true 'tell' for what's to come in the market and economy—that's just not been the case for the past two years," she said. "The 10-year (Treasury) yield has remained a true tell. The Russell 2000 definitely has been more accurate than the transports."
Still, few expect any major changes ahead for the index. While companies may come and go, the base of rail, air and ground travel will remain.
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Blitzer chuckled when asked if he thought drones could change the index but did say he could foresee a satellite-launching company get there in the next quarter century.
"It's a pretty wide selection of items that, without these companies, nothing would move other than electronics and the Internet," he said. "I think the general mix is likely to remain."
—By Jeff Cox, finance editor, CNBC.com