[TylerJewell]

For those worrying about concentration ... the market can get even more concentrated than it is now. In the 1880s, 80% of the market was related to railroads. That concentration always mean reverts, but it could take some time.

[danaris]

I feel like the situation in the 1880s was in a very, very different environment to today, though. How many public companies even were there 140 years ago...? (I actually tried to find this out just now with some quick searching, and wasn't able to find anything that looked relevant, so solid data would be helpful...)

Particularly in the latter part of the 20th century, the number of companies that choose to go public seems to have increased quite a bit—and, at the same time, there's been a huge wave of consolidation, meaning that even if there are fewer public companies than there would be without that, a higher share of the total economy is likely to be made up of public companies.