When adjusted for inflation. The graph (based on data from Robert Shiller) emphasizes the point that houses are consumable items composed of consumable items - "Houses are ordinary consumable goods: wood, stone and metal bound pieced together through labor. There's no reason to believe they should enjoy a special rate of return distinct from those for, say, apples and shoes."
The bottom line is that houses should be bought (or not bought) based on a individualized calculation of its utilitarian value - not as an "investment" to profit from.
Via Smart Money.