In trading on Wednesday, shares of the PowerShares Build America Bond Portfolio ETF ( BAB) entered into oversold territory, changing hands as low as $29.25 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 PowerShares Build America Bond Portfolio, the RSI reading has hit 26.8 — by comparison, the RSI reading for the S&P 500 is currently 44.2. A bullish investor could look at BAB's 26.8 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), BAB's low point in its 52 week range is $28.89 per share, with $31.42 as the 52 week high point — that compares with a last trade of $29.32. PowerShares Build America Bond Portfolio shares are currently trading down about 1% on the day.