The trend is your friend until it ends.© royyimzy/stock.adobe.com, © guteksk7/stock.adobe.com, © Oleksandr Delyk/stock.adobe.com; Photo illustration Encyclopædia Britannica, IncTop Questions What is Dow theory? Dow theory is a framework for understanding market trends and timing based on the analysis of market movements, originally developed by Charles Dow. How does Dow theory influence technical analysis? Dow theory serves as a foundation for technical analysis by providing principles for analyzing market trends and price movements. What are the key components of Dow theory? Key components of Dow Theory include the identification of primary, secondary, and minor trends, and the importance of volume and market indexes in confirming trends. Show MoreWhat do the Dow Jones Industrial Average, the Wall Street Journal, and technical analysis have in common? All three stem from one financial journalist named Charles Dow. He invented the Dow Jones averages, cofounded the newspaper that became the WSJ, and laid the groundwork for modern theories of technical analysis.

　　As a journalist/analyst working on Wall Street in the late 19th century, Charles Dow sought to deliver the clearest and most accurate interpretation of stock market movements in his editorials. His writings, posthumously combined, formed the basis of what became known as Dow theory. Its core principles reflect Dow’s analytical insights into the behavior of markets.

　　The six core principles of Dow theoryAlthough Charles Dow didn’t intentionally set out to create a theory, his editorials used an exploratory approach to economic and business matters, as if trying to figure out the undercurrents that made the markets tick. Over time, this patchwork of insights began to show recurrent themes concerning market behavior.

　　After Dow died in 1902, several analysts, including George Bishop (author of the 1960 book Charles H. Dow and the Dow Theory), gathered these themes and pieced together what is now known as Dow theory. Dow theory gained attention in the late 1950s when Richard Russell began publishing the Dow Theory Letters, which became the longest-running investment newsletter continuously written by a single author by the time of his death in 2015. 

　　#1: The stock market discounts all known informationInvestors collectively take action (buying or selling) based on all available information—economic, political, social, or company related. In this way, Dow’s insights were echoed decades later (with slight variation) in the efficient market hypothesis, which was introduced by economist Eugene Fama in his 1965 dissertation.

　　How to interpret and use it: Market movements are the result of investors attempting to “price in” expectations about a company, sector, or economy. Try to figure out what those expectations are and be prepared to either move with the crowd, if you think they’re correct, or take a contrarian view if you think they’re wrong. In other words, you can follow the trend or fight the trend.

　　#2: The market has three movementsDow observed three types of movements in the stock market:

　　Daily fluctuations are the day-to-day movement of prices that typically occur within a narrow price range; they’re also called “tertiary trends.”Longer swings are pullbacks within the primary trend that can last 20 to 40 days; they’re also called “secondary trends.”The main movement is also called the “primary trend.” The main movement describes bull trends, bear trends, and sideways ranges (non-trending markets), which can last for years.How to interpret and use it: If you’re a long-term investor, try to distinguish the main movement, or primary trend, from the smaller swings. It’s an easy principle to understand, but it’s not always easy to do. Secondary and tertiary trends can present trading opportunities, such as “buying the dip” or timing an entry or exit, but it takes diligence and discipline to be a trend trader.

　　Are you an investor or a trader? Or perhaps a bit of both?Encyclopædia Britannica, Inc.#3: Primary trends have three phases: accumulation, public participation, and distributionThese phases describe the progression of a bull market. (They’re also present during bear markets, but in reverse order.)

　　Accumulation. Informed investors (“the smart money”) begin buying stocks ahead of the general public.Public participation. Seeing the emergence of a new bull trend, the broader market joins in, causing strong upward price movement.Distribution. The smart money begins selling positions or shorting the market as the general public, driven by bullish sentiment, continues to buy.How to interpret and use it: As legendary investor Warren Buffett has often said, “Be fearful when others are greedy, and be greedy when others are fearful.” Recognizing these three phases in real time can help you move with the smart money rather than after it.

　　 #4: Indexes must confirm each otherTwo of the indexes Dow created—the industrial average (later named the Dow Jones Industrial Average, or DJIA) and the railroad average (later named the Dow Jones Transportation Average, or DJTA)—should be moving in the same direction in order to confirm a trend in the broader market. In the modern era, we typically include the S&P 500 and the Nasdaq Composite for a more comprehensive view of the broader market.

　　How to interpret and use it: The DJIA, S&P 500, and Nasdaq are correlated enough to confirm the state of the broader market. Keep an eye on all three, and make sure they agree when forming an opinion on the market’s main movement. Divergence among indexes may signal that the prevailing trend is about to change. Index divergence is also used to spot signs of sector rotation, in which the market may shift (for example) from growth to value, or from cyclical to defensive stocks.

　　#5: Volume must confirm the trendIf a market is trending higher, the volume of buying should be steadily increasing; if a market is declining, selling pressure should also be increasing. A divergence between volume and price action signals a weak trend and a potential reversal.

　　How to interpret and use it: Volume divergence is a key indicator in technical analysis. If volume doesn’t precede or support a price trend, then it may signal a potential pullback (up or down) from the current trend. You can use these to time entries (aka buy the dip) or take profits. This can be a tricky thing to do, even for veteran market technicians, as the ebb and flow of volume can sometimes generate false signals.

　　#6: A trend remains in effect until there is a clear reversalA primary trend is considered intact until price action signals an apparent reversal and is confirmed by other correlated indexes and/or signals.

　　How to interpret and use it: Spotting the end of a trend is a technical analysis skill that can complement fundamental analysis (i.e., analyzing company earnings, financial statements, and economic trends). There are many ways to spot a trend breaking down—the disruption of key support and resistance levels, divergence between price and volume and momentum, and various chart patterns. It takes a blend of art and science, but once you get the hang of it, identifying reversals can give you an extra layer of confidence when you’re looking to buy or sell.

　　The bottom lineCharles Dow passed away more than a century ago, but his memory lives on. Dow theory represents the roots of technical analysis—a way of understanding the markets through price behavior rather than financial statements alone. Like all technical analysis, it requires a degree of subjectivity in interpreting price data. But when used alongside fundamental analysis, Dow theory can expand your strategic and tactical tool kit, offering a more comprehensive view of the market.