Speculation last week of an impending new iPhone triggered a 70% increase in the number of owners trying to unload their current smartphones, online auctioneer eBay said.
Smartphone trade-in offers at eBay's Instant Sale site during the period July 30-Aug. 1 were 70% higher than the same three-day span of the week before, said eBay on Thursday.
Instant Sale generates quotes for used iPhones, iPads and other electronic devices.
Although Apple is expected to unveil a new iPhone this fall, until recently most experts believed the company would repeat the schedule it used in 2011. That would have marked Oct. 2 as the public launch date and Oct. 12 as the first day of sales.
On July 31, however, a little-known website called iMore.com claimed that the new iPhone will debut Sept. 12. Others, including the Wall Street Journal's All Things D blog, also pegged the Sept. 12 kick-off and, like iMore.com, said the phone will go on sale Sept. 21.
eBay attributed the spike in Instant Sale quotes to the July 31 news of a September launch.
In the three days following the news, eBay's Instant Sales generated 100,000 trade-in offers, with the 16GB iPhone 4S the most frequently jettisoned model.
On Sunday, Instant Sale quoted $299 for a 16GB iPhone 4S able to connect to AT&T's network, or $289 for the same model on Verizon.
It's not unusual for rumors of an Apple iPhone or iPad refresh to lift trade-in volume. Last February, as speculation circulated about a March 7 event Apple had scheduled -- but not divulged its purpose -- iPad owners pushed tablet trade-ins to record levels, said Gazelle, one of several companies that purchase used devices.
Gazelle and its ilk refurbish the devices, then resell them on eBay and Amazon.com, and to wholesalers, some of whom ship them overseas for sale in emerging markets.
Current sellers are trying to get the best price for their used phones, as values usually fall as soon as a vendor shows a new model. Last spring, iPad 2 trade-in values dropped 23% after Apple unveiled the new iPad.
Gazelle's Sunday price for an AT&T 16GB iPhone 4S was $277, while NextWorth, another used smartphone buyer, offered $263 for the same model.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.