In trading on Monday, shares of the FTSE RAFI Developed Markets ex-U.S. Portfolio ETF ( PXF) entered into oversold territory, changing hands as low as $35.731 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 FTSE RAFI Developed Markets ex-U.S. Portfolio, the RSI reading has hit 29.2 — by comparison, the RSI reading for the S&P 500 is currently 35.3. A bullish investor could look at PXF's 29.2 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), PXF's low point in its 52 week range is $29.48 per share, with $40.87 as the 52 week high point — that compares with a last trade of $35.78. FTSE RAFI Developed Markets ex-U.S. Portfolio shares are currently trading off about 2.4% on the day.