SellCell has recently released a report saying how iPhone 12 models have a slower depreciation rate compared to the iPhone 11 models.

Six months after the iPhone 12 was launched its value depreciated by around 34.5%. In comparison, the iPhone 11 models have lost its value by 43.8% in the same timeframe. It shows that the newer iPhone lineup has a 9.3% advantage over its predecessors 6 months after the smartphones launched.
The iPhone 12 launch may have depreciated the iPhone 11 model value- it lost 8% in three months and 10% within nine months, and continues to do so.
In the iPhone 11 lineup the iPhone 11 shows the least depreciation value at 31.7%, which is 17.5% less compared to the iPhone 11 Pro and 9% to the rest. In the iPhone 12 lineup the iPhone 12 mini lost the most at 41%, nine percent more than its iPhone 12 counterparts.