Keep in mind that "owning stock" isn't well-defined though, that could mean (a) own individual shares (narrowest), (b) owns shares or ETFs (broader), (c) owns mutual funds.

But that still doesn't address my point. It's a lot bigger when both private sector, and public, pensions are included.

This issue is near and dear to my heart because I grew up in Illinois (now living in California) and am watching the budget battle unfold there. They have a huge pension funding gap, and the returns of the stock market are going to have a very direct, real effect on how much tax the state has to collect to fund the pensions.