Onions have no futures market, yet their price volatility makes the swings in oil prices look tame.

MP: The chart above shows the monthly percent changes in spot prices for crude oil and onions between January 2000 and March 2012. During that period, onion prices have been about 7 times more volatile than oil prices, based on the differences in: a) mean monthly price changes (7.7% for onions vs. 1.3% for oil), and b) the standard deviations of monthly price changes (59.4% for onions vs. 8.6% for oil).

Update: The chart below compares the monthly percent changes in spot prices for onions and corn over the same period as onions and oil prices above, as an exercise in comparing the volatility of the prices of two agricultural commodities. One might argue that a comparison of oil and onion prices might not be valid if there are differences in agricultural commodity prices and energy prices. The fact that the volatility of onion prices is so much greater than the volatility of corn prices lends further statistical support to the notion that markets with futures trading like corn have lower price volatility than markets without futures contracts like onions.