Contrarians look to buy or sell against prevailing trends. For example, when bearishness dominates investor sentiment, perhaps it’s time to consider increasing your equity exposure. Contrarian trading isn’t easy. The question is: how to measure investor sentiment? One objective measure of whether the sentiment is bullish or bearish is given by the P/C ratio— total put options volume relative to call options volume. When P/C ratio is at extremes, price reversals can occur. A trader doesn’t have to be an options trader to potentially benefit from its insights. Think or Swim allows you to plot the Put/Call Ratio, to view the following data: $PCALL: All of the listed stocks $PCI: The Dow Jones Industrial Average $PCRL: The stocks in the Russell 2000 $PCSP: The stocks in the S&P 500® $PCND: The stocks in the NASDAQ® 100 The figures below show the case when P/C ratio caught the mid-term trend reversal of SP500 on 6/4/19.