In 1995 the car population of the US passed 200,000,000. I don't know the total for the world or any other country.
But automobiles have this really peculiar characteristic; they wear out. Of course people buy more, but those wear out too. So every time we buy more cars the economists add them to GDP. But do those cars that wore out get subtracted from anywhere?
Guess what? The entire economics profession can't do grade school algebra.
When was the last time you heard them talk about
NET Domestic Product?
http://discussions.pbs.org/viewtopic.pbs?t=28529
psik