Smoothed County Population Estimates for 2000-2009

Methodology --- County Totals

County population counts for April 2010 from the 2010 Census were released by the Census Bureau in March of 2011. Smoothed estimates of the population of North Carolina Counties for July 1, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 and 2009 were released in April 2011. These estimates are based on a process of smoothing the revised estimates prepared annually to more nearly match the trendline between the values for April 1, 2000 and April 1, 2010 from the 2000 and 2010 Censuses.

Basic Technique, Revised Estimates

For these estimates, the county boundaries are those in effect for the 2000 federal census, including changes released by the Census Bureau through December of 2010. The state estimate was produced by adjusting the 2000-2009 state estimates for North Carolina released in early 2010 by the United States Bureau of the Census for changes in major institutional populations. The county estimates are averages of two sets of estimates, a set of modified Census Bureau estimates, and a set of alternative estimates produced by this office.

Modified Census Bureau Estimates

In 2010, the Population Division of the United States Bureau of the Census released their revised 2000-2010 county population estimates for North Carolina. They used an administrative records technique similar to the 1990's technique of the same name.

Alternative Estimates

Two basic procedures were used to build these estimates. First, population 65 years of age and older is estimated. In the past, changes in the number of MEDICARE enrollees during the estimate period were used to measure changes in the population 65 years of age and older. For this year, as for last year, because of problems getting consistent MEDICARE data for years after 2003, this office used the 65+ population from the modified Census Bureau estimates mentioned above.

Second, a standard ratio/correlation method is used to estimate the population aged 0-64. The data series used were automobile and truck registrations (X1), school enrollment in grades 1 through 8 (X2), and a three year sum of births (X3). For 2009, the three year sum of births was the sum of final calendar year values for 2007, 2008, and 2009; for 2000, the sum of final calendar year values for 1998, 1999, and 2000. The prediction equation for each North Carolina county is given by

y = -0.00606 + 0.52041 * X1 + 0.27723 * X2 + 0.20262 * X3,

where y represents the estimated ratio of percentage shares of nongroup quarters population and each of the series indicators (X1, X2, and X3) represents the ratio of percentage shares of the associated variable. The equation coefficients were derived by least squares regression, using series indicator and population values for 1990 and 2000. The results of this equation were adjusted for the extra 1/4 year of the estimate period by linearly expanding the change in y from the assumed 2000 value of 1.0. The nongroup quarters 0-64 population estimate derived from this equation was combined with independent estimates of the population of military barracks, college dormitories, and other institutions to yield the estimate of the total 0-64 population.

The state estimates for 2000-2009 were the adjusted ones mentioned above.

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Last Update: May 10, 2011