The Dow Theory is one of the oldest and most influential concepts in technical analysis, originally developed by Charles H. Dow, the co-founder of Dow Jones & Company and the first editor of The Wall Street Journal. It is based on the premise that the stock market reflects all available information, and that the movement of stock prices follows identifiable trends that can be analyzed to forecast future price movements. Dow Theory provides a systematic framework for understanding the long-term behavior of stock prices, making it particularly relevant for investors and portfolio managers who rely on trend analysis to make investment decisions. At the core of Dow Theory are several key principles. The first principle is that the market discounts everything. This means that all information—whether public or private, known or anticipated—gets incorporated into stock prices immediately. Economic factors, corporate earnings, political developments, and even investor psychology are considered to be already reflected in the market. According to this idea, price movements are not random but are influenced by real underlying conditions, making the study of past price trends meaningful for forecasting future trends. The second principle emphasizes that the market has three types of movements: primary trends, secondary trends, and minor trends. Primary trends are long-term movements lasting from several months to several years, representing the overall direction of the market, which can be bullish (uptrend) or bearish (downtrend). Secondary trends, also called intermediate trends, are shorter-term reversals or corrections within the primary trend, often lasting from weeks to months. These trends typically retrace a portion of the primary movement, often between one-third to two-thirds of the previous price swing. Minor trends are short-term fluctuations lasting a few days to weeks, reflecting market noise and speculative activity. Understanding these three types of trends helps investors differentiate between temporary market reactions and long-term directional movements. Another important tenet of Dow Theory is that the stock market consists of two averages that should confirm each other: the industrial average and the transportation average. The industrial average represents the performance of major industrial companies, while the transportation average reflects the health of transport and shipping companies, which are indicative of goods movement and economic activity. According to the theory, a primary trend is considered valid only