NVI

Summary

Negative Volume Index: a running cumulative index that changes only on days when
volume falls versus the prior day, compounding that day's percentage price change.
The premise is that quiet, low-volume days reflect the actions of well-informed
"smart money", so NVI is read as a proxy for that cohort's positioning.

Formula

NVI[startIdx] = 1000

For each subsequent bar i:

NVI[i] = NVI[i-1] + ( inVolume[i] < inVolume[i-1]
                      ? ((inClose[i] - inClose[i-1]) / inClose[i-1]) * NVI[i-1]
                      : 0 )

The index carries forward unchanged on bars whose volume did not fall (and on the
degenerate case of a zero previous close, which would otherwise divide by zero).

Inputs

• inClose — Close price of each bar
• inVolume — Volume of each bar

Outputs

• outReal — Cumulative negative volume index (seeded at 1000)

Properties

Numerical Stability: Path-Dependent

Display Flags
☐ Overlap Input
✅ Independent Y-Axis i
☐ Candlestick

Implementation

TA-Lib Definition: nvi.c · nvi.yaml

Native	File
C	ta_NVI.c
Rust	nvi.rs
Java	Core_NVI.java

TA-Lib is also available for Python, R and more using a wrapper.

Aliases

Negative Volume Index

References

• Norman G. Fosback, Stock Market Logic, The Institute for Econometric Research (ISBN 0917604482)