I can't imagine it would. I assume you're talking about rental properties? The number of homes owned for sale by investors at any given time is probably small, given that flipping a house is pretty fast (several months?), and houses in major metro areas tend to go from listing to under-agreement in a matter of days. Or is there some phenomenon of investors buying properties and holding on to them for sale, rather than for rent?

>The homeownership rate is the proportion of households that is owner-occupied.

The main cause for the increase since 1900 was the invention of the mortgage, which did not really exist until about 1950. Loans existed, but the exact mortgage structure is a modern invention. It increased home ownership rates but also housing costs due to higher demand.