In trading on Monday, shares of the Guggenheim S&P Global Water Index ETF ( CGW) entered into oversold territory, changing hands as low as $22.35 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 Guggenheim S&P Global Water Index, the RSI reading has hit 26.6 — by comparison, the RSI reading for the S&P 500 is currently 35.3. A bullish investor could look at CGW's 26.6 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), CGW's low point in its 52 week range is $19.54 per share, with $25.22 as the 52 week high point — that compares with a last trade of $22.40. Guggenheim S&P Global Water Index shares are currently trading off about 2% on the day.