> I interpret that to mean someone purchasing a home today must have roughly twice the resources to purchase the same home as someone in the past
Case-Shiller is not adjusted for inflation. In addition, it does not take into account interest rates. Until recently, mortgage rates were extremely low. It takes less resources to pay the mortgage on a $1,000,000 house at 3% interest than it does to pay the mortgage on a $250,000 home at 19% interest (which is where interest rates topped out at in the 1980's).
Inflation: according to several calculators online, $100 in 2003 is roughly $170 (rounding up) in 2023 dollars. So 70% over 20 years. Meanwhile Case-Shiller has grown 123% over the same period.
Interest rate: in 2003 the interest rate was in the high 5's. Today it's in the mid 6's. So let's call it a wash.[1]
What I'm saying is, today someone is buying the same house, at roughly the same interest rate as someone twenty years ago except that today 1) the house is twenty years older, 2) it's also about 30% more expensive after adjusting for inflation.
I grant that means the person needs fewer than 2x the resources, but my point still stands.
Case-Shiller is not adjusted for inflation. In addition, it does not take into account interest rates. Until recently, mortgage rates were extremely low. It takes less resources to pay the mortgage on a $1,000,000 house at 3% interest than it does to pay the mortgage on a $250,000 home at 19% interest (which is where interest rates topped out at in the 1980's).