In addition to the other replies, there is a serious argument to be made for keeping a car longer or buying used in terms of environmental impact. MPG improveme

In addition to the other replies, there is a serious argument to be made for keeping a car longer or buying used in terms of environmental impact. MPG improvements have been minor enough to not offset the huge environmental cost of manufacturing the car itself. It's better to keep the old Explorer that still runs than to buy a new Prius. I'd be interested to see a study about whether the last twenty years of safety gadgets have actually reduced accident casualties significantly. My thought is that at least as far as collision performance, things have been pretty well understood that whole time.