Is the house price based on a similar sized and quality of house or does it reflect the tendency to build bigger and more luxurious dwellings? To ensure the graph can be kept in perspective, can you add a line that plots the changing size and level of appointments of the average new house over the years and then lets see what it looks like. I think we will find that the current graph is more an indicator of human behaviour than some economic revelation. Another question, why start the graph at 1986? What would it look like if it started at 1945? The starting point is critical, it should ideally be at a point where conditions have been stable for a period of time. It's the same when people argue that rainfall has declined in the last 30 years, the 70's were a period of above average rain. They couldn't make the same argument for rainfall declining over say the last 40 years because the starting point was a period of below average rain.
