Trends are confirmed by volume

Dow believed that volume confirmed price trends. When prices move on low volume, there could be many different explanations why. An overly aggressive seller could be present for example. But when price movements are accompanied by high volume, Dow believed this represented the “true” market view. If many participants are active in a particular security, and the price moves significantly in one direction, Dow maintained that this was the direction in which the market anticipated continued movement. To him, it was a signal that a trend is developing.

From this tenet it follows that volume should increase when the price moves in the direction of the trend and decrease when the price moves in the opposite direction of the trend. For example, in an uptrend, volume should increase when the price rises and fall when the price falls. The reason for this is that the uptrend shows strength when volume increases because traders are more willing to buy an asset in the belief that the upward momentum will continue. Low volume during the corrective periods signals that most traders are not willing to close their positions because they believe the momentum of the primary trend will continue.

Conversely, if volume runs counter to the trend, it is a sign of weakness in the existing trend. For example, if the market is in an uptrend but volume is weak on the up move, it is a signal that buying is starting to dissipate. If buyers start to leave the market or turn into sellers, there is little chance that the market will continue its upward trend. The same is true for increased volume on down days, which is an indication that more and more participants are becoming sellers in the market.

According to Dow theory, once a trend has been confirmed by volume, the majority of money in the market should be moving with the trend and not against it.

Note:
Menurut Dow, pergerakan harga banyak dipengaruhi naik turunya Volume. Volume merupakan salah satu penyebab harga bergerak dalam trend
jika seandainya harga bergerak dalam bullish trend maka harus diikuti oleh peningkatan volume juga. Alasannya adalah, suatu kondisi bullish akan disebut strong bullish jika diikuti oleh peningkatan volume, peningkatan volume ini menunjukkan adanya peningkatan kepercayaan di market bahwa akan terjadi penguatan lebih lanjut.

Tapi jika seandainya dalam kondisi bullish malah terjadi penurunan volume yang cukup signifikan secara tidak langsung sudah menujukkan akan adanya reversal trend. (Orang-orang sudah siap take profit)

Bahasa sederhananya adalah jika seandainya ada kondisi harga breakout maka sebaiknya diikuti juga oleh kondisi volume yang break high juga