The Dow Theory is a well-known financial theory developed by Charles Dow, the founder of Dow Jones & Company, in the late 19th century. The theory suggests that the market is in an upward trend if one of its averages, such as the Dow Jones Industrial Average (DJIA) or the Dow Jones Transportation Average (DJTA), advances above a previous important high and is accompanied or followed by a similar advance in another average. This phenomenon is known as "confirmation" and is seen as a bullish signal by investors. According to the Dow Theory, if the DJIA and DJTA are both moving in the same direction, it suggests a strong economy, as companies are producing goods and shipping them to consumers. Conversely, if one average is moving in one direction and the other in the opposite direction, it can signal a weakening economy. Overall, the Dow Theory is still widely followed by investors today as a way to analyze market trends and make informed investment decisions.