In trading on Friday, shares of the iShares Real Estate 50 ETF ( FTY) entered into oversold territory, changing hands as low as $43.2099 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of iShares Real Estate 50, the RSI reading has hit 28.7 — by comparison, the RSI reading for the S&P 500 is currently 49.3. A bullish investor could look at FTY's 28.7 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), FTY's low point in its 52 week range is $37.37 per share, with $45.58 as the 52 week high point — that compares with a last trade of $43.33. iShares Real Estate 50 shares are currently trading off about 2.9% on the day.