Anarcho vs. Monopoly Capitalism - Quantitative Studies?

Hi - I've become interested in Rothbard's ideas re anarcho as opposed
to monopoly capitalism, which I find very appealing. I would like to
find out if this question has been studied quantitatively - ie if there

are ways of quantifying the extent to which the US economy has
veered towards and away from monopoly capitalism over the years,
and evaluated the performance of the economy under both systems.

Maybe one approach would be to categorize companies by size, and
to look at the percentages of americans employed by small
companies and mega- corporations etc. Of course this is just a very
rough measure at best.

Does anyone here have any ideas about this question?

Thanks,
Tim Howells

.