[breischl]

Since they're mostly not public, I'd say probably very few.

From TFA:

> To make things even more complex, many of these large companies are not traded publicly on the stock market, meaning their total number of holdings is not easily available to the public. Because Invitation Homes is publicly traded

[em500]

Invitation Homes (NYSE: INVH) is part of S&P500, so I'd say very many (owning a tiny share). Ownership of INVH is overwhelmingly institutional (investment/mutual/retirement funds): https://finance.yahoo.com/quote/INVH/holders

[pfgallagher]

Some of the largest investors in private equity REITs are retirement funds.