Negative Volume Index (NVI)

What Is Negative Volume Index (NVI)?

The negative volume index (NVI) is a technical indication line that integrates volume and price to graphically show how price movements are affected by down volume days.

Understanding Negative Volume Index (NVI)

The negative volume index (NVI) can be used in conjunction with the positive volume index (PVI). Both indexes were first developed by Paul Dysart in the 1930s and gained popularity in the 1970s after being spotlighted in Norman Fosback’s book entitled "Stock Market Logic."

The positive and negative volume indexes are trendlines that can help an investor follow how a security’s price is changing with effects from volume. PVI and NVI trendlines are typically available through advanced technical charting software programs such as MetaStock and EquityFeedWorkstation. Trendlines are usually added below a candlestick pattern similar to the visualization of volume bar charts.

Negative volume index trendlines can potentially be the best trendlines for following mainstream, smart money movements typically characterized by institutional investors. Positive volume index trendlines are usually more broadly associated with high volume market trending effects, which are known to be more heavily influenced by both smart money and noise traders.

NVI can be useful after a price comes down from high volume trading. Low volume days can show how institutional money and mainstream investors are trading a security. Generally it is best to follow both the NVI and PVI together, as overall they represent how price is being influenced by volume.

Negative Volume Index (NVI) Calculations

Calculation of the NVI depends on how volume for a single day compares with the previous day’s trading volume. NVI will only change when volume has decreased from one day to the next. Thus, if current volume is higher, there is no change. If volume is lower than the previous day then NVI is calculated using the following equation:

NVI = PNVI + ( TCP  −  YCP YCP × PNVI ) where: PNVI = Previous NVI TCP = Today’s closing price YCP = Yesterday’s closing price \begin{aligned} &\text{NVI}=\text{PNVI}+\left(\frac{\text{TCP }-\text{ YCP}}{\text{YCP}}\times\text{PNVI}\right)\\ &\textbf{where:}\\ &\text{PNVI = Previous NVI}\\ &\text{TCP = Today's closing price}\\ &\text{YCP = Yesterday's closing price}\\ \end{aligned} NVI=PNVI+(YCPTCP − YCP×PNVI)where:PNVI = Previous NVITCP = Today’s closing priceYCP = Yesterday’s closing price

If NVI is higher, it means that the price is increasing with decreased volume. If NVI is lower it means that the price is decreasing as fewer investors trade the security.

Calculation of the PVI depends on variables similar to those in the NVI. If current volume is greater than the previous day's volume, PVI = Previous PVI + {[(Today's Closing Price-Yesterday's Closing Price)/Yesterday's Closing Price] x Previous PVI}. If current volume is lower than the previous day's volume, PVI is unchanged. If PVI is higher it means that the price is gaining with high volume. If PVI is lower it means that the price is decreasing with high volume. Generally, the PVI will see significant changes when the release of unanticipated news about a company causes a high volume of trading.