I will admit to being a bit out of my depth with newer Porsche values. I'm deeply involved with classic cars, so depreciation in modern cars simply doesn't come up for me often. Thankfully the folks at JP&Co. released a handy video charting the depreciation of water-cooled 911 Carreras. The video covers the relationship between age, mileage, and even options on the value of a used 911 Carrera.
While the depreciation curve looks more or less like you'd expect (see the chart below), several other factors are taken into consideration. Porsche's legendary option list appears to add very little to the value of a used 911, for example. Though this may be a sticking point for sellers, this can mean getting very good value from a highly optioned car.
The video notes a 17.5% depreciation hit in a 911's first year, followed by another 11.5% after the second year. After that the curve generally flattens out. The earliest water cooled Porsches are currently at or around the bottom of their depreciation curve.
Classic 911 values are currently all over the place, and even total project cars are commanding high prices. It is good to see that modern 911 values are more predictable, which should help putting prospective Porsche-philes behind the wheel.