Every day on CNBC-TV they show a 200-day moving average line superimposed on the stock price history. It seems they give great credence to this manufactured line as it represents 10 months of price action. What is it? Does it really mean anything?
The line represents the addition of the closing prices of that particular stock, mutual fund or index for the past 200 trading sessions that have been added up and divided by 200. That is then placed on the chart at that point. For example if the price of the equity started at zero and went up exactly one point for 200 days the average would be 100. A dot is then place on the chart at 100 even though the equity price is now at 200. Each day the new closing price is added after dropping off price number 1 and the new group is added up and divided by 200. This is done each day. Nothing complicated.
Does this mean anything?
This is considered to be a very useful technical indicator, but like all technical indicators you must understand how to use it. There is one rule for any technical indicator: no single one is a Holy Grail for predicting future price action of a stock, fund or index. WAIT! Don't throw out the baby with the bath water.
The 200-day MA is not a predictor, but it does establish the current trend of whatever you wish to measure that has a recurring event. You can use it for the average price of housing, cost of gold, global weather temperature, medical costs, etc., etc. that can then be plotted on a chart.
You don't have to stay with 200 days. You may modify it to any number of days or time periods you wish from two on out past 200. Many technical analysts use 10, 20, 50, 100 and then plot these on the same chart simultaneously to see when one crosses over another. These are called oscillators and thousands of traders use them to determine buy and sell signals.
Because the 200-day MA is composed of 200 price entries it has been determined that it works best when used with something that has many factors represented. In the stock market this is indexes and mutual funds. Mutual funds are composed of many stocks or bonds and the price action of any single equity does not cause a major price swing.
If you will keep in mind that the 200-day MA will show only the major long term trend it can be a very useful investment tool.