Apple Inc. (NASDAQ:AAPL)’s iPhone 6 and 6 Plus are still popular both in the U.S and China, its two biggest markets.

In a study done by Piper Jaffray, iPhone 6 and 6 Plus resale prices were shown to be significantly higher in its post launch period than the post-launch period of the iPhone 5 and 5c. From this statistical conclusion, it seems there is more demand for the iPhone 6 and 6 Plus in later months than there was for the iPhone 5 and 5c. This is important because it suggests that certain aspects in the iPhone 6 and 6 Plus make it a better product, a product that can achieve continued success without relying on the fad mentality of consumers.

As for the study itself, U.S iPhone 6 and 6 Plus units were going for 72% of their original retail price nine months after launch. On the other hand, iPhone 5s and 5c were sold at 65% and 53% of their retail price during the same post-launch period, respectively.

A similar trend was discovered in China, where eight months after launch, both iPhone 6 and 6 Plus models, up for sale on Taobao, went for 73% of the new retail price. Those statistics compare to 65 percent and 53 percent for iPhone 5s and 5c over the same time period, respectively.

China was very similar, iPhone 6 and 6 Plus on sale through Taobao went for 73 percent of its new retail price eight months after launch. Conversely, the numbers were 53% and 65% for iPhone 5c and 5s, respectively.

Tracking resale prices is a tactic used by Piper Jaffray to measure demand for products, specifically Samsung and Apple electronics. The data comes from Ebay and Taobao, auction websites were data can be collected with ease. To then create a model with which relative demand can be understood, Piper Jaffray takes the last 50 phones bought and indexes it in comparison to the current retail price.

According Smarter Analyst, Piper Jaffray analyst Gene Munster, warned that estimating iPhone popularity from resale price is not a flawless way of meaurement. There are risks in correlating demand with retail price, there are too many factors not accounted for that affect both figures of demand and resale price. Yet Munster sees a trend of resale price being at least slightly correlated and thus of some importance.

As for Apple, Munster stated that “We believe iPhone will continue to gain share at the high end smart phone market, which, despite tough comps starting in Dec-15, should move shares of AAPL higher.” The company sold a record 35.2 million iPhones in the third quarter of 2014 while selling 74.5 million iPhones in the first quarter of 2015 and 61.2 million in its second quarter.

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