JAN. 18, 2017 – Today the CBOE SKEW Index (SKEW) closed at 143.43, its highest value since June 2016. CBOE SKEW Index values, which are calculated from weighted strips of out-of-the-money S&P 500 options, rise to higher levels as investors become more fearful of a “black swan” event — an unexpected event of large magnitude and consequence.
The value of SKEW increases with the tail risk of S&P 500 returns. If there were no tail risk expectations, SKEW would be equal to 100.
The FAQ on the SKEW Index notes that –
“The price of S&P 500 skewness is inconvenient to use directly as an index because it is typically a small negative number, for example -.8, -2.3, or -4.3. SKEW converts this price as follows: SKEW = 100 – 10 * price of skewness. With this definition, a price of -2.1 translates to a SKEW value of 121. S&P 500 options with 30 days to expiration are generally unavailable. SKEW is therefore interpolated from two “SKEW” values at the maturities of nearby and second nearby options with at least 8 days left to expiration.”
HIGHER SKEW VALUES IN RECENT YEARS
The average value of SKEW (since the beginning of its data history in 1990) has been 118.4. Prior to 2014, the highest average daily closing value in a year for the SKEW Index was 122.5, but in each of the years 2014, 2015, 2016, and year-to-date 2017, the average daily closing level for the SKEW Index was 127.5 or higher.
30 ½ YEARS — BENCHMARK INDEXES AND SPX PUT OPTIONS
For investors who wish to learn more about hypothetical long-term performance of strategies that use index options, CBOE provides more than 30 strategy benchmark indexes. Note in the two charts below that the left tail risk was higher for the S&P 500 Index than it was for two indexes that use SPX put options – the CBOE S&P 500 PutWrite Index (PUT) sells cash-secured SPX options, while the CBOE S&P 500 5% Put Protection Index (PPUT) buys out-of-the-money protective put options on the SPX Index.