BOX 4-4

Illustrative Calculation for Suppressing Table Cells with Large Sampling Error, 1-Year ACS Period Estimates

Assume a city of population 100,000, with 2,000 school-age children in a particular population group (e.g., Hispanic).

First Pass of Table

Ratio of Family Income to Poverty Threshold

Percent Chldren in Category

Coefficient of Variation (CV)

Below poverty threshold

15.0

60.4

100–149 percent of poverty

10.0

76.1

150–199 percent of poverty

10.0

76.1

200–249 percent of poverty

10.0

76.1

250–299 percent of poverty

10.0

76.1

300–349 percent of poverty

20.0

50.7

350 percent or more of poverty

25.0

43.9

What is the result?

  • Median CV is 76.1.

  • The table may not be released because the median CV is greater than 61.0.

Second Pass of Table after Combining Categories

Ratio of Family Income to Poverty Threshold

Percent Chldren in Category

Coefficient of Variation (CV)

Below poverty threshold

15.0

60.4

100–199 percent of poverty

20.0

50.7

200–299 percent of poverty

20.0

50.7

300–349 percent of poverty

20.0

50.7

350 percent or more of poverty

25.0

43.9

What is the result?

  • Median CV is 50.7.

  • The table may be released because the median CV is less than 61.0.

Recommendation 4-10: The Census Bureau should monitor the extent of collapsing of cells that is performed in different tables to meet minimum precision standards of 1-year and 3-year period tabulations from the ACS and assess the implications for comparisons among geographic areas and over time. After sufficient information has been gleaned about the extent of data collapsing, the Census Bureau, in consultation with data users, should assess whether its collapsing rules are sound or should be modified for one or more subject areas.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement