Dow Theory says the trend, Demand, Supply. It help traders to understand the market better and identify price and volume movements more accurately. Line chart is used for Dow Theory. The Line Chart with a minimum of two years data is used to forecast the trend for two to three months. If the sequence is formed with Higher Bottom and Higher Top with high volume, it is a Bullish trend. If the sequence is formed with Lower Bottom and Lower Top with high volume, it is Bearish trend.