The Positive Volume Index by Norman Fosback is the companion to his Negative Volume Index. The two are used to identify bull and bear markets.
Positive Volume Index makes the assumption that the uninformed crowd dominates trading on active days. On days when volume increases, the crowd-following "uninformed" investors are in the market.
The PVI displays what the not-so-smart-money is doing just as the Negative Volume Index displays what the smart money is doing. However the PVI is not a contrarian indicator. While Fosback says the PVI shows what the uninformed may be doing, it still trends in the same direction as price.