Chart of the Day commentary puts it as follows:
[The] chart presents the median single-family home price divided by the price of one ounce of gold. This results in the home / gold ratio or the cost of the median single-family home in ounces of gold. For example, it currently takes 153 ounces of gold to buy the median single-family home. This is considerably less that the 601 ounces it took back in 2001. When priced in gold, the median single-family home is down 75% from its 2001 peak and remains well within the confines of its five-year accelerated downtrend.
As mentioned in previous posts, gold is a measure of long-term wealth; therefore is a good relative indicator when comparing different products/service on an intertemporal basis. Based on the trajectory of the graph we are headed to levels seen around 1979-1980. This means that house prices will fall further.