TDEX TDEX is a real-time index, available on major broker platforms like thinkorswim, that calculates and standardizes the cost of SPY puts at three standard deviations OTM. A TDEX reading of 15 would mean that a put (one standard deviation out of the money at 30 DTE) would cost 15% of the underlying security. What this shows is a chart of how expensive tail protection is, which is creating a hedge for unlikely but catastrophic events. By comparing it to the ballpark of past values, we can see how relatively expensive tail protection is as compared to the past. As an example of how to use this strategically, if TDEX is higher than normal, then this indicates the presence of skew edge on the tail-end, which suggests that it would be worth writing deep OTM wingtips if holding (or wanting to buy) long puts. TDEX whitepaper: <https://nations.com/wp-content/uploads/2020/01/Nations-TailDex-Tail-Risk-Indexes.pdf> Related articles SDEX Vanna Rule of 16 / Rule of 7.2 0DTE Wingtip