A security price's rate of change is a measure of momentum, which indicates how much the price has changed between two points in time. The time-frame used can be virtually anything you prefer. For short-term changes, you might chose a day, week or month. For long-term changes you might assess a year or multiple years. Regardless of the time-frame, the calculation remains the same.
1. Get the current and historic price of the stock. The historic price can be as far back as you like. You can get these quotes from your stock broker, or websites such as MSN.com, Finance.Yahoo.com or Google.com/finance.
2. Subtract historic price from the current price. As an example, if stock ABC is trading at $80.00 per share, but was trading at $75.00 per share a week ago, then the difference would be $5.
3. Divide this difference by the historic price to calculation the rate of change. In the example, dividing $5 by $75.00 gives you a 0.0667 rate of change, or 6.67 percent.
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