In investing, financial markets are commonly believed to have market trends that can be classified as primary trends, secondary trends (short-term), and secular trends (long-term). This belief is generally consistent with the practice of technical analysis and broadly inconsistent with the standard academic view of financial markets, the efficient market hypothesis.Fact: date=June 2008 Another commonly held academic viewpoint is that market prices follow a random walk model and that any apparent past 'trends' are purely an accumulation of random variations.

However, the assumption that market prices move in trends is one of the major components of technical analysis,John J. Murphy, Technical Analysis of the Financial Markets (New York Institute of Finance, 1999), p. 2. and consideration of market trends is common to most Wall Street investors. Market trends are described as sustained movements in market prices over a period of time. The terms bull market and bear market describe upward and downward movements respectively: this can relate either to the market as a whole or to specific sectors and securities (stocks). The expressions "bullish" and "bearish" can also mean optimistic and pessimistic respectively ("bullish on technology stocks," or "bearish on gold", etc).

Primary market trends

A primary trend has broad support throughout the entire market or market sector and lasts for a year or more.

Bull market

A bull market tends to be associated with increasing investor confidence, motivating investors to buy in anticipation of future price increases and future capital gains. In describing financial market behavior, the largest group of market participants is often referred to, metaphorically, as a herd. This is especially relevant to participants in bull markets since bulls are herding animals. A bull market is also sometimes described as a bull run. Dow Theory attempts to describe the character of these market movements.

India's BSE Index SENSEX was in a bull run for almost one year from January 2007 to January 2008 as it increased from 14,000 points to 21,000 points. Another notable and recent bull market was in the 1990s when the U.S. and many other global financial markets rose rapidly. The United States was described as being in a secular (long term) bull market from about 1983 to late 2007, with brief upsets including the Panic of 1987 and the NASDAQ crash of 2000-2002.

Bear market

A bear market is described as being accompanied by widespread pessimism. Investors anticipating further losses are often motivated to sell, with negative sentiment feeding on itself in a vicious circle. The most famous bear market in history was preceded by the Wall Street Crash of 1929 and lasted from 1930 to 1932, marking the start of the Great Depression. A milder, low-level, long-term bear market occurred from about 1973 to 1982, encompassing the stagflation of U.S. economy, the 1970's energy crisis, and the high unemployment of the early 1980s.