The line chart below shows the published volatility, the 20-day underlying volatility based on MTM price, the 20-day underlying volatility based on high and low differences and the ‘average’ 20-day volatility between the two 20-day volatility measures for the JUL16WMAZ contract. Published volatility has slipped by 4% over the past 3 weeks whilst our other measurements on 20-day volatility decreased by -2.73% from 19.5% to 16.42%,- 2.5% from 25.3% to 22.8% and 2.62% from 22.2% to 19.6% respectfully.