Comment by rmah

First, you are correct. However, the reason GDP is used as a proxy metric for economic growth because it's convenient. Doing so does make a few assumptions though, foremost of which is that the structure of the economy will change very little from year to year. If that is so, than a rise in GDP should correspond to a rise in economic prosperity (and by extension wealth). Thus, using GDP change to measure changes in prosperity works (more or less) year by year. but the longer the periods you compare (5 years, 10 years, 20 years), the less meaningful the number becomes.