The plot does not convey all the available data. Here is a different plot that is derived from the same dataset.
Black lines are like error bars - representing highest and lowest values of VIX futures. The red band inside is the middle 50% of the data, i.e. form first to third quartile. Since VIX futures were listed most of the trading action took place somewhere between 15 and 30. Most of the lower quartile action happened in 2004-2006, and most of the upper quartile happened in 2008.
With longer term VIX futures trading at over 30, and recent realized volatility at about 20% I think the futures will come down a bit to I personally have bearish bets in January - although the reason for trade was based on my forecasting model, and not on the analysis above.
Now here comes what I think is the most interesting part: same plot, now every historical futures value is a dot.
The VIX futures can be partitioned into three regimes. If that is not clear from previous plot - here is a histogram.
These three regimes are not present in the VIX index data, they are only seen in VIX futures. Using k-means of log values the centers are:
- Low 14.55 +/- 1.60
- Middle 24.31 +/- 2.83
- High 37.19 +/- 6.45