The put to call ratio is simply the ratio of short options over long options in the S&P 500. What sticks out to me is that the ratio saw its second highest level in December of 2018. While a bottom of .3 percent would likely signal irrational exuberance as had been suffered in 2007, it seems since 2012 a bottom target is .6 percent. While the market melts up under low volume, this could be an interesting chart to keep an eye on as a signal before a major correction.