In trading on Monday, shares of the iShares NYSE 100 ETF ( NY) entered into oversold territory, changing hands as low as $79.25 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 NYSE 100, the RSI reading has hit 27.9 — by comparison, the RSI reading for the S&P 500 is currently 33.7. A bullish investor could look at NY's 27.9 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), NY's low point in its 52 week range is $70.53 per share, with $85.68 as the 52 week high point — that compares with a last trade of $79.25. iShares NYSE 100 shares are currently trading off about 1.9% on the day.