In trading on Thursday, shares of the SPDR Bloomberg Barclays Mortgage Backed Bond ETF ( MBG) entered into oversold territory, changing hands as low as $26.6135 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 SPDR Bloomberg Barclays Mortgage Backed Bond, the RSI reading has hit 29.3 — by comparison, the RSI reading for the S&P 500 is currently 61.9. A bullish investor could look at MBG's 29.3 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), MBG's low point in its 52 week range is $26.6135 per share, with $27.36 as the 52 week high point — that compares with a last trade of $26.61. SPDR Bloomberg Barclays Mortgage Backed Bond shares are currently trading off about 0.7% on the day.