One tool traders use to identify a trend in stock price is the trend line. It is a line drawn between the high and low point for a stock over a period of time. If the stock price goes up from $10 to $20 to $30 over a three year period, the analyst can plot a line from $10 to $30 starting in year one and ending in year three. The first year marks the first plot in the series, it is the baseline price of $10. The second year represents the beginning of the trend at $20, and the third year marks the continuation, or possibly the end of the trend, at $30. In this way, trend lines can be used to either predict the next data point along the trend or look for a reversal of the trend.