I'm sure there are more qualified people to speculate on that than me. 

I believe it's been driven by years of ridiculously low interest rates, a huge and prolonged commodities boom/bubble along with foreign investor speculators.  

Real Estate speculation at it's best here

I've heard a ton of rumors and speculation about shadow inventory, but at the rate that rental properties are increasing in value in my area, I think much of this is exaggeration.

Everything would be speculation and hypothetical scenarios.

My competition is doctor-daddies buying something for their little angels at outrageous prices, speculators betting on big appreciation, and 'hobbyist' investors who don't understand the numbers.

This is speculation and in this market that is a hard thing to do.

I know your market is way overheated and people are buying on speculation of price increases.

I invest in lower income neighborhoods to build up substantial cashflow and middle to upper middle class neighborhoods for speculative appreciation.

Still, it is best to not waste too much time in speculation...