apacheguy I was very careful to say that I use this number based on my purchase patterns (trade in on new when my car is typically 3yrs/40K miles). This is only a snapshot in time. Trade in a year earlier and the depreciation per mile is more, trade a year later and it will be less. I just need a number that sets my own expectations so that I properly discount the accident damaged car for the milage on it when I replace it. I do not expect my number to work for everyone.