*Macmillan Science Library: Mathematics*. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.

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## Making Projections

The 6 billion mentioned in the opening paragraph is an estimate created by a mathematical model using data from every country in the world. The data used to make the current estimate are actually about 2 years old. So the number on the clock is really a mathematical projection from the 2-year-old data. The following example is greatly oversimplified, but it illustrates the principle involved in such projections.

Suppose that you had high-quality data showing that the population of a certain city was one million at the beginning of the year 2000 and that this city's population had historically grown at about 2 percent per year. If you assume that there are no extraordinary events that would change this growth rate, you could calculate as follows. Two percent of 1 million is 20,000, so at the beginning of 2001, you would project the city's population to be 1,020,000. Then 2 percent of 1,020,000 is 20,400, which would...

This section contains 1,506 words(approx. 6 pages at 300 words per page) |