FYI: Many investors think of real estate investment trusts (REITs) as a distinct asset class, because in aggregate they have historically had relatively low correlation with stocks and bonds, and their returns were not well-explained by the single-factor CAPM model.
For example, during the period January 1978 through September 2016, the monthly correlation of the Dow Jones U.S. Select REIT Index with the S&P 500 was 0.58, and with five-year Treasurys, it was just 0.07.
Regards,
Ted
http://www.etf.com/sections/index-investor-corner/swedroe-reits-arent-special?nopaging=1