It starts at 0, but it is based on the volume of the stocks which are trading either above or below yesterday's closing price. So as we hover around yesterday's index close, we have intertwined lines, but that is obviously not representative of the actual sentiment since 10:30am...
ii think its based on up ticks and down ticks from last trade with volume as an amplifier or muter so when the intertwine or crossover is happening there are no larger bears or bulls playing,flat day, when the one say dvol is flatlining,no sellers,downticks, and the uvol is climbing a hill ,it shows strong bullishness,trendday...i find it very useful,to each his own
I haven't really used it but it does seem very useful to determine a trend day - ammo's uvol/dvol charts are great
symbol sources for futures: http://cfe.cboe.com/tradecfe/ticker_vix.aspx or the index is just IB: VIX from CBOE DTN: VIX.XO esignal: $VIX yahoo: ^VIX something new I'm adding into strats - not sure yet - like to keep it simple, adding it means removing something else.