Real estate always has been a key allocation in investment portfolios but, prior to the advent of stock exchange-listed REITs, it meant making an investment in an illiquid asset. Stock exchange-listed REITs combine the investment benefits of real estate with the benefits of a liquid market, which has become progressively more so. The average daily dollar trading volume of the U.S. listed REIT market in July was $7.1 billion, up from $4.2 billion five years earlier in July 2011, and $2.0 billion in July 2006.