You're asking the wrong question. The answer is 10%

The interesting question is power-to-weight, which was (apparently) a direct result of EPA regulations that were enacted in 1975. The below article, which I found from a search engine copying your question and looking at a few results, is an interesting read.

Ignoring all that, the actual question would be: how have car sizes and weights changed _in this region_ during this period of time. Sizes and weights of cars in brasil have little bearing to accidents in the PNW, for example.

https://carbuzz.com/new-vehicles-bigger-heavier-more-powerfu...