slumlords are a symptom of an ailing system, page-48

I fail to see what that has to do with anything...

As your rent increases over the years, the % return you are getting on your initial purchase price increases above that 4% average you speak of. The 4% average is comparing current property price/value with current rental income... once you have made your purchase, the figure you paid never changes, but as your rent increase over the years, so then does the yield.

Do you understand that?