The population of the United States changes on a continual basis. Knowing this rate of change is important to both the government and private businesses. The population growth or decline in an area can help a company decide where it wishes to locate its office, based on the potential amount of customers and employees alike. The trends could indicate the area is an expanding market, or a declining one, both valuable pieces of information.
Choose the location for which you want to calculate the population growth rate. This could be for the entire United States, a specific region, state or smaller area, depending on the purpose of your calculation and how you will use that data. This example will focus on the city of Las Vegas, Nevada.
Determine the years you want to compare. This could be the population growth rate from one year to another, or you might want to determine what the increase or decrease was over a longer span of time, such as 10 or even 50 years. As an example, let's calculate the population change from 2000 to 2007 for Las Vegas, Nevada.
Determine the population in the starting year for your population growth rate comparison. The U.S. Census Bureau has a website with information to help you find these numbers for the location you are comparing (see Resources). The starting population in Las Vegas, Nevada, for the year 2000, according to the U.S. Census Bureau website, was 478,434.
Determine the population for the ending date for the area. Once again, this can be found at the U.S. Census Bureau's website. The population in Las Vegas in 2007, according to the U.S. Census Bureau website, was 558,880.
Subtract the population from your starting date from the population from your ending date. This will tell you how much the population has changed. A positive number indicates the population has grown, and a negative one indicates the population has dropped in that time frame. Take 558,880 (Las Vegas population for 2007) and subtract 478,434 (Las Vegas population for 2000). This gives you a positive change in population of 80,446 people.
Divide your result in Step 5 by the population of your starting year. This will tell you the population rate growth or decline rate in a decimal form. Multiply it by 100 to convert that rate to a percentage. In our example, divide the population change of 80,446 by the starting population of 478,434. This gives you a decimal answer of .1681. Multiply this decimal by 100, and you have a positive population rate growth from 2000 to 2007 in Las Vegas of 16.81 percent.
Tip

To get directly to the page to look up populations by city, state, or zip code, select the "People & Households" link on the U.S. Census Bureau's website, and then click on the "Population Finder" link.
Tip

Do not divide the difference you calculate between your starting and ending years by the population in the ending year. That will not provide you the percentage of increase or decrease from the starting year, instead it will use the ending year and provide an inaccurate statistic.
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