The ARV will perhaps be the easiest and closest thing to which you'll have data for. 

@Ed Morrison Rentometer has a pretty horrible data model.

(i.e. are big complexes or small ones driving the data?)

Whereas the vacancy rate increases so does the median cap rate.The data above was collected from the census american community survey and is computed at the tract level.Vacancy rates where computed first and split into cohorts that increment 0.1 percent.

Maybe they think they're being helpful, but it's actually quite the opposite.I work in data analysis/research for a living, so I'm pretty anal about this stuff.

I get all the data from my real estate agent.

Blue means increase, red decrease.The data is from the census american community survey 

Or databases which I might use to find these data?

Can't comment on the rental income without any data like NOI, expenses etc.

I know it's large but your data shows it's mind-bogglingly HUGE!