The Wilder's Relative Strength Index is a rate of change oscillator. Relative Strength Index does not compare the relative performance of one stock to another, instead it compares the price of a stock to itself. A reading of 70% or higher is generally an overbought position. Conversely, values near the 30% level should be considered an indication the situation has become oversold. When the stock price is trending, use Relative Strength Index to trade strictly with the trend. The Wilder's Relative Strength Index was developed by J. Welles Wilder, Jr.