The 53% decline in oil prices since September 22, 2008, without a 20% rally is the biggest since 1986 (based on available daily data). The week of Sep. 16 to Sep. 22, oil rallied 20%+ after dropping 37% from the July 3, 2008 high.
In all, the price of oil has dropped more than 61% since the July peak, and likely to break lower given the ongoing conditions in the market.
Chart: Bespoke Investment Group