You guys are right, but also, if the mean lifetime of Porsche cars would be eg. 10 years, then the advertised metric would have to be 52%, given the historic pr

You guys are right, but also, if the mean lifetime of Porsche cars would be eg. 10 years, then the advertised metric would have to be 52%, given the historic production curve. This was just a spiel to reverse engineer the mean lifetime given this marketing number. (And yes, there are lots of caveats...) avg_lifetime -> on_the_road_ratio (given historic production curve) 10 -> 0.519 11 -> 0.545 12 -> 0.567 13 -> 0.585 14 -> 0.603 15 -> 0.625 16 -> 0.647 17 -> 0.668 18 -> 0.688 19 -> 0.705 20 -> 0.720 21 -> 0.733 22 -> 0.745 23 -> 0.756 24 -> 0.766