Data Usage Notes

ACS Margin of Error

All ACS data are survey-based estimates and have an error of estimation and associated margin of error (MOE). By adding and subtracting the margin of error from the point estimate, you produce the range around it called the confidence interval. With 90 percent confidence, the interval 15,120 +/- 1,377 (the MOE for this estimate) contains the true Klein ISD population estimate for the population 5 to 9 years of age. This information means that if the survey is conducted 100 times, the number of respondents in this age group would range between 15,120-1,377 and 15,120+1,377 most (90 percent) of the time.

Estimates of size 100 or smaller may have a margin of error larger than the estimate. An estimate of 10,000 may have a MOE of 1,000-1,200; an estimate of 20,000 may have a MOE of 1,400-1,600. Precisely computed MOE values are available for all ACS estimates.

Using ACS Multi-year Estimates

1 - Interview Collection Periods

The American Community Survey (ACS) 1-year estimates are based on data collected in one specific calendar year. For the 2007 ACS estimates, the data from all sample interviews that were obtained between January 1, 2007 and December 31, 2007 are pooled to produce the 1-year data products. Multiyear ACS estimates are based on the data collected over multiple consecutive calendar years. Therefore, using the 2005 - 2007 ACS estimates as an example, the data from sample interviews collected between January 1, 2005 and December 31, 2007 are pooled to produce this 3-year product.

2 - Geographic Boundaries

For the ACS 1-year estimates, the geography is based on the boundaries defined on January 1 of the year being tabulated. For the ACS 3-year estimates, the geography is based on the boundaries defined on January 1 of the final year in the 3-year period. Likewise for ACS 5-year estimates, boundaries are defined as of the final year in the 5-year period. For example, Amarillo City, Texas annexed some territory in both 2005 and 2006. The 2005 1-year estimates were published without the boundary changes because they all occurred after January 1, 2005. The 2006 1-year estimates were published with the 2005 boundary changes because they were added prior to January 1, 2006. The 2007 and the 2005 - 2007 estimates were published with all the boundary changes. Note that the Census Bureau does not plan to update the 2005 and 2006 1-year estimates using the January 1, 2007 boundaries.

3 - Weighting Methodology

The ACS 1-year estimates of total housing units are controlled to conform to estimates of housing units from the Census Bureau's Population Estimates Program. The ACS 1-year estimates of total population are controlled by age, sex, race, and Hispanic origin to conform to the official population estimates from the Population Estimates Program. These controls are for the reference date of July 1 of the tabulation year and are updated annually. The ACS 3-year estimates are controlled to conform to a simple average over the 3-year period of the housing and population estimates from the Population Estimates Program. The version of the Population Estimates Program estimates used to obtain these averages are the ones corresponding to the last year of the period. For example, the controls used for the 2005 - 2007 weighting would be equal to the simple average of the 2005, 2006, and 2007 estimates that were produced for the year 2007. Thus, the controls for the 3-year period may not equal the simple average of the controls used to produce the ACS 1-year estimates.

4 - Inflation Adjustments

Monetary values for the ACS 1-year, 3-year, and 5-year estimates are inflation adjusted to the final year of the period. For example, the 2005 - 2007 ACS 3-year estimates are tabulated using 2007 adjusted dollars. These adjustments use the national Consumer Price Index (CPI) since a regional-based CPI is not available for the entire country.

5 - Some Tables not Tabulated for all Areas

Data for some whole tables are not provided in the ACS 05-07 estimates for specific geographic areas.

- This is the result of the inability to tabulate reliable data for this universe/table.

- Data cells in these tables are shown as all zeroes; the values are not true zeroes.

Page url: http://proximityone.com/sddynamics/guide/index.htm?data_usage_notes.htm