When people talk about the size of an economy, they often refer to the GDP or changes to it, but seldom refer to the Net National Wealth. Obviously there are some superficial differences:
- GDP is Gross not Net
- GDP is Domestic not National (Within borders vs. owned by citizens)
- GDP is $\Delta$Capital whereas NNW is theoretically all the capital stock owned by a country's citizens.
It appears the US switched from publishing GNP to GDP relatively recently (~1970), which seems like a less direct measure of its citizens economic welfare, but even that seems like an already abstracted measure from NNW.
So again, what are the differences between the two measures as economic indices that makes one more desirable (or at least discussed) than the other.