World economic growth metrics? (was Re: [extropy-chat] The emergence of AI)

[Brett Paatsch]

Robin Hanson wrote:

> Economic growth is the fully recursive self-improvement of 
> the world economy as a whole.

Apologies if this is taken too far out of context but does it actually
make sense to speak of a single world economy as something that
has a growth that can be meaningfully measured?  

It seems to me that currently the world is not a homogeneous system
under a single set of laws. This means that many of the transactions
that take place between persons (both natural and legal) on the planet
do so on a basis that is anything but fully voluntary for many people.  

I am not an economist so my question is almost certainly naive but I 
wonder what growth metrics would be tracked in measuring the 
growth of something like a world economy as opposed to a merely 
national one?  

Brett Paatsch