In trading on Friday, shares of the iShares Retail Real Estate Capped ETF ( RTL) entered into oversold territory, changing hands as low as $39.0601 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 Retail Real Estate Capped, the RSI reading has hit 27.3 — by comparison, the RSI reading for the S&P 500 is currently 49.3. A bullish investor could look at RTL's 27.3 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), RTL's low point in its 52 week range is $33.98 per share, with $41.12 as the 52 week high point — that compares with a last trade of $39.06. iShares Retail Real Estate Capped shares are currently trading off about 3.1% on the day.