when pvi increases or decreases it means that price changes are being driven by high volumes conversely when nvi increases or decreases it means that prices are fluctuating with little effect from volume 
calculating the positive volume indexif current volume is greater than the previous day s volume if current volume is lower than the previous day s volume pvi is unchanged if the current volume is less than the previous day s volume if the current volume is higher than the previous day s volume nvi is unchanged many investors believe that noise trading is a significant factor in the positive volume index therefore the negative volume index is often followed for its insight into professional traders market activity investopedia does not provide tax investment or financial services and advice the information is presented without consideration of the investment objectives risk tolerance or financial circumstances of any specific investor and might not be suitable for all investors investing involves risk including the possible loss of principal 