While most people don't buy the latest iPhone every year, there are certainly some who do. And for those who are eyeing the new iPhone 13 this fall, online marketplace SellCell has good news.

During the first six months of sales, the site reports that iPhone 11 series devices lost 43.8% of their original value. During the same period, however, iPhone 12 smartphones lost an average of 34.5%

This figure is also exacerbated by the unpopular iPhone 12 mini. according to SellCell's data, the 5.4-inch mini lost 41% of its value after six months, while the iPhone 12 Pro Max has only dropped 28.9%.

If you have your heart set on the upcoming iPhone 13, the key question is when should you sell last year's device? Based on the iPhone 11 data, I'm guessing the sweet spot is month 9. iPhone 12 was released on October 23, 2020. which means, in effect, now.

As can be seen from the table above, the resale value of the iPhone 11 plummets at the 12-month mark, which is around the time the iPhone 12 was introduced (thanks to the Covid-based delay, it appeared in October rather than Apple's traditional September event, but in this case the correlation (close enough to likely imply causation).

Even if you miss that sweet spot, iPhone values seem to deteriorate fairly slowly after the initial new-model shock, and you can still buy an iPhone 11 device at the right price 21 months after launch.

If you are an iPhone owner and find the drop in value a bit depressing, take solace in the fact that it could be worse: according to another analysis by SellCell, the Samsung Galaxy S21, one of the best Android phones, is expected to sell for less than the iPhone 12 losing resale value considerably faster than the iPhone 12.

Apple is so confident in the iPhone 13's sales that one report says the company plans to manufacture 20% more units than this time last year and is hoping for a possible cobid resurgence.

Rumors suggest that the iPhone 13 is expected to offer a faster A15 Bionic processor, improved 5G, a larger battery, a smaller notch, possible Touch ID support, and many camera upgrades including portrait video mode . The iPhone 13 Pro, however, could draw attention with its rumored 120Hz ProMotion display.