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### Working with an Exponential Trend

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An exponential trend is one that rises or falls at an increasingly higher rate. Fads often exhibit this kind of behavior. A product might sell steadily but unspectacularly for a while, but then word starts getting around—perhaps because of a mention in the newspaper or on television—and sales start to rise. If these new customers enjoy the product, they tell their friends about it, and those people purchase the product, too. They tell their friends, the media notice that everyone's talking about this product, and a bona fide fad ensues.

This is called an exponential trend because, as a graph, it looks much like a number being raised to successively higher values of an exponent (for example, 10^{1}, 10^{2}, 10^{3}, and so on). This is often modeled using the constant e (approximately 2.71828), which is the base of the natural logarithm. Figure 15.20 shows a worksheet that uses the `EXP()` function in column B to return e raised to the successive powers in column A. The chart shows the results as a classic exponential curve.