He is referring this study: http://www.conferenceboard.ca/hcp/hot-topics/caninequality.a...
It has a chart of INFLATION-ADJUSTED median after-tax income in 2009 dollars, from 1976 to 2009. He then takes a figure for 1984 from this chart, around $48500, and proceeds to compare it to prices in 1984 dollars, without converting them to 2009 dollars.
So from a house price of 100k in 1984, he infers it was only 2x times median income then. While in fact, he needs to convert 100k in 2009 dollars and get around 200k and 4x times median income.