Volume & money flowPositive Volume Index · PVI
The mirror of NVI — a cumulative line that changes only on higher-volume days, tracking the crowd.
Works best in trending marketsEngine-computed on a fixed sample series
What it is
The Positive Volume Index is a cumulative indicator that changes only on days when trading volume rises from the day before, on the theory that it tracks what the uninformed crowd is doing — because the crowd is most active precisely when volume surges. It answers the question of where the herd is pushing price, and, read against its mirror the Negative Volume Index, whether the crowd and the so-called smart money agree. Devised within the framework Paul Dysart pioneered and Norman Fosback later formalized, PVI runs as a single line that steps up or down on busy days and sits still on quiet ones. It is a big-picture, regime-oriented tool rather than a timing trigger. For a beginner it is best understood as a running tally of price behavior on high-participation days, meant to reveal what the mass of ordinary investors is doing.
How it is calculated
PVI starts from an arbitrary base value, commonly 100 or 1,000, and updates only when today's volume is greater than yesterday's volume. On those higher-volume days it adds the day's percentage price change to the running total — in practice the index is multiplied by one plus the day's percentage change, so it compounds with price on active sessions. On days when volume is equal to or lower than the prior day, the index holds flat, carrying yesterday's value unchanged. Over time this produces a line that moves in step with price on the busy days and ignores the quiet ones entirely, isolating crowd-driven behavior. Its counterpart, the Negative Volume Index, does the opposite, changing only on lower-volume days, so the two together partition price action by participation.
Reading it, step by step
A rising PVI means price is advancing on the high-volume days when the crowd is most engaged, while a falling PVI means the busy days are down days. The classic interpretation compares PVI to its own one-year moving average, typically a 255-day exponential average, as a regime gauge: PVI above that average leans bullish, below it leans bearish. Fosback's historical work found PVI a weaker bull-market indicator than NVI but a useful one, associating PVI above its one-year average with a moderately elevated probability of a bull market. The tool is most informative when contrasted with NVI: when both rise, broad strength is present, but a rising PVI alongside a falling NVI warns that only the crowd is buying while informed money stays out. Read the slope and the relationship to the long average, not the absolute level, which is arbitrary.
Best timeframes and settings
PVI is a long-horizon, big-picture indicator best applied to daily data on broad market indices, with the 255-day, one-year average as its standard reference line. It suits position traders and investors framing the primary trend, not day traders — its signals unfold over months, and it spends long stretches flat. The 255-day average can be shortened to make the regime read more responsive, but doing so sacrifices the very long-cycle perspective the indicator exists to provide. It works far better on indices and broad baskets than on individual stocks, where idiosyncratic volume muddies the crowd interpretation. There is little to tune beyond the averaging length, and the tool is meant to be slow and strategic.
When and where to use it
Use PVI as a strategic regime filter for the broad market, favoring the long side when it holds above its one-year average and turning defensive when it drops below, always in concert with NVI for the fuller picture. It is designed for stock-market indices and is most meaningful there rather than on single names or intraday charts. Avoid it entirely for short-term timing, since it is useless for entries and exits measured in days. The crowd-versus-smart-money framing is a heuristic from an earlier market era, so it should inform context rather than dictate trades. Reach for it when you want a slow, volume-partitioned read on whether the overall market environment favors risk-taking.
Strategies that use it
The primary strategy is regime filtering: treat PVI above its 255-day average as a green light to hold long exposure and PVI below it as a caution flag to reduce risk, using it to bias rather than time decisions. The paired approach reads PVI alongside NVI, taking the most bullish stance when both trend up above their averages and the most cautious when both roll over, and treating divergences between them as warnings that crowd and smart money disagree. A confirmation use overlays PVI's regime read on a separate trend-following or asset-allocation model, tilting position sizes with the volume regime rather than trading PVI crossovers directly. Because the indicator is slow, all of these are strategic overlays for position traders rather than mechanical entry systems.
Combining it with other indicators
The Negative Volume Index is PVI's essential companion, since the two are designed to be read together to compare crowd and smart-money behavior. On-Balance Volume and the Accumulation/Distribution line add other volume-based perspectives on whether money is flowing in or out. A broad trend filter such as the index's 200-day moving average corroborates PVI's regime signal. Breadth measures like advance-decline lines round out the participation picture at the market level. The recurring logic is to use PVI as one lens in a suite of volume and breadth tools that together describe the health of the primary trend, never as a standalone trigger.
Where it fails
PVI's central weakness is that it is slow and coarse — useless for short-term timing, prone to long flat stretches, and best confined to broad indices rather than single stocks. The crowd-versus-smart-money premise underlying it is a heuristic rather than a law, and on modern, algorithm-dominated markets the clean split between high-volume crowd days and low-volume informed days is far fuzzier than when Dysart and Fosback devised the concept. Traders err by applying it to individual stocks, by using it for entries, or by trusting its regime signal without the corroboration of NVI and price. The remedy is to keep it in its lane as a slow, index-level regime filter read in tandem with NVI and confirmed by trend. Expecting precise turning-point signals from it inverts its purpose.
A worked example
Suppose a broad equity index sees a string of sessions where the up days happen to coincide with heavier volume and the down days with lighter volume. On each higher-volume up day PVI compounds higher — from a base of 1,000 to 1,006 after a 0.6 percent gain, then to about 1,014 after a further 0.8 percent gain — while the quiet down days leave it untouched, so the line climbs and pulls above its 255-day average, signaling a crowd-driven bullish regime. If NVI is simultaneously above its own one-year average, both crowd and smart money are aligned, and a position trader holds long exposure with confidence. But if instead PVI keeps rising while NVI turns down beneath its average, the message flips to caution — the crowd is chasing on the busy days while informed money quietly steps back, a classic late-cycle divergence that argues for trimming risk rather than adding.