Since 1890. The Eleventh Census was the first to ask whether you owned your home, and whether you still owed on it. Before that, there was no national measure of American homeownership at all.
The homeownership rate did not exist. For a century the census counted people, not tenure. No one could state what share of American families owned their homes, or how many carried a mortgage. Housing ran on anecdote.
The Eleventh Census, taken in 1890, added two new questions to every household. Was the home owned or rented? And if owned, was it free from what the census called mortgage incumbrance? Mortgaged families then reported the debt, the property value, and the interest rate.
The results filled two volumes: one on real estate mortgages, and one titled Farms and Homes: Proprietorship and Indebtedness in the United States. It was the first national measurement of American homeownership, and of American mortgage debt, in the same instrument.
The 1890 census was also the first tabulated by machine, on punched cards designed by Herman Hollerith. The tabulating company he founded was later folded into the business that took the name IBM in 1924. The birth of national housing data and the birth of modern data processing are the same event.
What gets counted gets funded. That first count set the baseline every housing number since is read against. Measurement is not a description of a market. It is a precondition for acting on one.
Note on precision: the Hollerith system is widely credited with cutting years off census processing. Figures vary depending on whether the population count or full publication is measured, so no specific figure is claimed here.
