What it means
Volume is simply the number of shares or contracts traded in a period. On its own it says little about direction, because heavy trading can happen in a rally or a sell-off.
Net volume adds direction by splitting volume into the part traded when prices rose and the part traded when prices fell. For a single stock, up volume is the trading done on price rises and down volume is the trading done on price falls.
For a whole market, the measure often compares the volume of advancing stocks with the volume of declining stocks. The difference is the net volume for the market on that day.
The idea behind it is that price moves backed by heavy trading are more convincing than those on thin trading. If a share climbs 3% on strong net buying volume, many analysts see this as a healthier signal than a 3% rise on very little volume.
Similarly, a market that falls with a large negative net volume suggests broad selling pressure. Net volume is the basis of several popular tools.
The on-balance volume indicator adds volume on up days and subtracts it on down days to build a running total, and the advance-decline volume line does something similar for the whole market. Traders use these to look for confirmation or warning signs, such as a rising price while net volume weakens.
The nuance is that the measure is not a prediction. It is based on classifying each trade or each day as up or down, which can be crude, and every trade has a buyer and a seller by definition.
Analysts treat it as one input among many, together with price trends, earnings and the wider economy. Because the numbers are easy to obtain, net volume features in many charting packages and daily market reports.
A reader of a financial news site may see a sentence such as the market rose on positive net volume without any further explanation. Now you know it simply means more of the day's trading took place on the way up than on the way down.
In practice
Real-world examples.
Example
A technical analyst at a brokerage notes that a bank's share price edged up 1%, but net volume was -450,000 shares. She tells clients that the rise lacks conviction and may not last. Two weeks later the shares fall back.
Example
A portfolio manager monitors the market-wide measure each evening. On a day when advancing stocks traded 2,400,000,000 shares and declining stocks traded 1,600,000,000, net volume is +800,000,000. He takes this as a sign of healthy participation and keeps his equity allocation unchanged.
Example
A day trader in a biotech company sees net volume turn sharply positive after a press release. She buys 2,000 shares at $8 and sets a stop-loss at $7.60 to limit the risk to $800. The net volume figure helps her decide when to enter but not when to exit.
Formula
Calculation
Net volume = up volume - down volume
Net volume ratio = net volume / total volume
On one trading day, shares in a mid-sized company changed hands 1,000,000 times in total, with 600,000 on upticks and 400,000 on downticks. Net volume = 600,000 - 400,000 = +200,000 shares. The net volume ratio is 200,000 / 1,000,000 = 20%, which points to moderately more buying than selling pressure. At a price of $15, the extra buying is worth about 200,000 x $15 = $3,000,000.Case study
Seen in the real world.
Orchard Lane Securities is a fictional brokerage, and this illustrative story shows how a trading desk might use net volume. Its research team tracked a manufacturing stock whose price had risen 12% over a month. The team noticed that net volume had fallen for three weeks in a row, even as the price rose.
They published a note warning that the rally was being driven by fewer and fewer buyers. Within a fortnight the stock dropped 9% after a disappointing sales update. The team did not claim to have predicted the news, but the divergence between price and net volume had been a useful reason for clients to review their holdings.
Watch out
Common mistakes.
- Treating net volume as a guaranteed forecast. It describes past trading and can give false signals.
- Believing buying volume can exceed selling volume. Every trade has both a buyer and a seller, so net volume reflects classification of trades, not a true imbalance of shares.
- Using it in isolation. It works better alongside price patterns, trend measures and company fundamentals.
Questions
People also ask.
How is net volume different from total volume?
Total volume counts all trading, while net volume subtracts down volume from up volume to show direction.
What is on-balance volume?
It is a running total that adds volume on days the price rises and subtracts it on days the price falls.
Is it useful for long-term investors?
It can add context, but it is mostly used for short and medium-term trading decisions.
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