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Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities (2015)

Chapter: Appendix B: Examples of Differences Between Census Counts and ACS Population Estimates

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Previous Chapter: Appendix A: Usability Analysis: Tract-Level 2008-2012 ACS Data

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Suggested Citation: "Appendix B: Examples of Differences Between Census Counts and ACS Population Estimates." National Research Council. 2015. Realizing the Potential of the American Community Survey: Challenges, Tradeoffs, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/21653.

Appendix B

Examples of Differences Between Census Counts and ACS Population Estimates

This appendix examines the magnitude of discrepancies between the 2010 census and 2008-2010 American Community Survey (ACS) counts for age-sex strata in a systematic selection of communities: Fort Wayne, Indiana; Sterling Heights, Michigan; San Clemente, California; Valparaiso, Indiana; Sunnyside, Washington; Rayne, Louisiana; and Ely, Nevada. Table B-1 shows the raw differences and Table B-2 shows the percentage differences. Many of the communities examined are the size of an average census tract. In many instances, the 2008-2012 ACS 5-year period estimates do not approximate the 2010 census results when 5-year age groups by sex are compared, and some comparisons include differences by factors as large as two.

For example, in Ely, Nevada (population 4,255), the ACS reported 201 females aged 30-34 while the census reported 103, a 95 percent difference. For males aged 15-19 years, the ACS reported 263 residents while the census reported 168, a 57 percent difference. For Rayne, Louisiana (population 7,953), the female population aged 35-39 years was reported in the ACS as 437 and in the census as 258; for all people aged 40-44, the ACS reported 153, and the census reported 257. Though not included in the table, similar differences appear in a sample of census tracts for the Bronx as well.

These problems are not confined to very small areas. For San Clemente, California (population 63,522), the number of females aged 85 and older in the ACS was 564, compared with 777 in the census, a 27 percent difference. For Fort Wayne, Indiana (population 253,691), the ACS reported

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2,206 males aged 80-84, and the census reported 1,862, a 19 percent difference. The ACS also reported 1,253 males aged 85 and older, and the census reported 1,450, a 14 percent difference. That is, the differences are found for both tract and city estimates for geographic areas that are smaller than the county level. Even with the difference in reference periods (point-in-time census estimates and 2008-2012 ACS estimates), differences of this magnitude in 5-year age groups are larger than what one would reasonably expect.

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TABLE B-1 Differences Between 2010 Census Counts and ACS 2008-2012 Population Estimates, by Sex and 5-Year Cohorts: Seven Cities

Population, by Sex and Age Cohorts	Fort Wayne, Indiana	Sterling Heights, Michigan	San Clemente, California	Valparaiso, Indiana	Sunnyside, Washington	Rayne, Louisiana	Ely, Nevada
Census Total Population	253,691	129,699	63,522	31,730	15,858	7,953	4,255
Male	666	–812	1,036	–147	86	–25	96
Under 5 years	–33	–355	1	95	–177	212	3
5 to 9 years	347	–359	–448	62	368	–118	41
10 to 14 years	–169	174	368	–96	94	–43	55
15 to 19 years	–205	18	295	45	–153	–32	–95
20 to 24 years	95	–18	252	187	–147	–71	42
25 to 29 years	161	–321	330	90	78	58	37
30 to 34 years	98	182	258	105	248	–26	43
35 to 39 years	499	347	–325	–16	–141	–71	–24
40 to 44 years	–193	–455	114	81	34	–410	–9
45 to 49 years	458	–49	218	44	104	22	9
50 to 54 years	–82	114	155	–174	–43	–32	–12
55 to 59 years	243	–150	83	–11	–40	–22	8
60 to 64 years	–460	–16	34	–27	–93	57	6
65 to 69 years	143	16	–54	84	–90	38	12
70 to 74 years	–41	65	–155	–165	33	–16	–5
75 to 79 years	–48	27	–82	17	58	50	36
80 to 84 years	–344	–144	25	12	22	–10	–33
85 years and older	197	112	–33	197	–69	20	–18

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Population, by Sex and Age Cohorts

Fort Wayne, Indiana

Sterling Heights, Michigan

San Clemente, California

Valparaiso, Indiana

Sunnyside, Washington

Rayne, Louisiana

Ely, Nevada

Female

–592

624

–701

106

–3

–77

Under 5 years

–203

539

–175

–69

157

5 to 9 years

245

–252

–171

10 to 14 years

–214

343

–398

–103

–24

15 to 19 years

305

436

321

–11

–47

–83

20 to 24 years

–165

–70

–49

–188

–49

25 to 29 years

–318

–142

288

–169

185

30 to 34 years

–27

–288

–147

105

–98

35 to 39 years

–54

–415

123

–179

40 to 44 years

130

131

–289

120

–37

104

–98

45 to 49 years

203

510

–150

–198

50 to 54 years

–171

119

–207

–32

–15

55 to 59 years

–2

–95

–159

–10

–24

–7

60 to 64 years

–82

224

–117

–81

–85

65 to 69 years

–59

–89

–11

–16

70 to 74 years

–134

–88

–54

–65

–42

75 to 79 years

–56

–73

155

–74

80 to 84 years

–114

–4

–12

–36

–48

85 years and older

–139

213

–80

–3

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Summary of 5-Year Cohorts
Maximum	499	539	510	321	368	212	60
Minimum	–460	–455	–448	–174	–198	–179	–98
Percentage of county population	71.4	15.4	2.1	19.3	6.5	12.9	42.4
Sampling rate	7.8	7.5	6.3	7.2	4.9	6.3	9.8
Unweighted sample size of population	19,764	9,748	3,981	2,276	775	499	415

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TABLE B-2 Percentage Differences Between 2010 Census Counts and ACS 2008-2012 Population Estimates, by Sex and 5-Year Cohorts: Seven Cities

Population, by Sex and Age Cohorts	Fort Wayne, Indiana	Sterling Heights, Michigan	San Clemente, California	Valparaiso, Indiana	Sunnyside, Washington	Rayne, Louisiana	Ely, Nevada
Total Population	0.0	–0.1	0.5	1.2	0.5	–0.2	4.4
Male	0.5	–1.3	3.2	1.2	1.1	–0.7	2.1
Under 5 years	–0.3	–9.7	0.0	–15.2	–16.9	72.9	35.0
5 to 9 years	3.7	–9.2	–19.5	9.5	42.2	–35.8	43.0
10 to 14 years	–1.8	4.1	17.0	6.5	11.9	–15.0	–56.5
15 to 19 years	–2.2	0.4	13.6	–7.5	–20.1	–10.7	34.4
20 to 24 years	1.1	–0.4	13.1	2.5	–22.2	–27.5	27.4
25 to 29 years	1.8	–8.0	16.7	13.6	13.1	25.7	38.7
30 to 34 years	1.1	4.6	15.3	8.1	43.2	–13.3	–22.4
35 to 39 years	6.2	8.3	–15.3	10.3	–29.6	–37.0	–7.7
40 to 44 years	–2.5	–10.5	4.7	–1.8	8.1	–17.2	5.5
45 to 49 years	5.5	–1.0	8.5	8.7	25.9	7.9	–6.9
50 to 54 years	–1.0	2.4	6.0	4.7	–13.0	–11.6	4.2
55 to 59 years	3.2	–3.5	3.9	–19.9	–14.7	–9.9	4.2
60 to 64 years	–7.7	–0.4	1.9	–1.5	–45.4	26.9	11.4
65 to 69 years	3.6	0.5	–4.2	–6.2	–55.2	25.9	–5.8
70 to 74 years	–1.5	3.2	–17.2	25.5	28.7	–13.8	50.7
75 to 79 years	–2.1	1.9	–12.1	–54.6	61.7	50.5	–70.2
80 to 84 years	–18.5	–13.7	4.7	6.5	28.9	–16.4	–51.4
85 years and older	13.6	12.5	–7.0	4.7	–78.4	44.4	–3.7

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Female	–0.5	0.9	–2.2	1.2	0.0	0.1	6.2
Under 5 years	–2.1	15.5	–9.1	11.6	16.4	23.1	27.6
5 to 9 years	2.7	–6.9	–8.0	–7.7	9.0	31.4	–18.2
10 to 14 years	–2.4	8.8	–18.8	2.3	1.2	33.3	–64.3
15 to 19 years	3.3	2.1	22.0	–8.6	–1.6	–17.2	47.6
20 to 24 years	0.9	–4.1	–4.4	16.9	–31.2	–21.0	35.1
25 to 29 years	–3.4	–3.4	16.6	–4.0	29.3	14.8	–95.1
30 to 34 years	–0.3	–7.2	–8.3	–16.7	1.4	6.5	37.2
35 to 39 years	1.1	–1.3	–18.5	10.7	25.9	–69.4	–77.8
40 to 44 years	1.7	2.9	–11.5	5.1	–8.4	40.5	16.9
45 to 49 years	0.8	4.0	19.6	12.6	–52.4	3.0	–8.5
50 to 54 years	–1.9	2.3	–8.5	–14.2	20.8	–10.7	4.5
55 to 59 years	0.0	–2.0	–7.4	5.8	–8.7	–2.7	5.4
60 to 64 years	–1.2	5.3	–6.4	–1.2	–38.6	7.3	15.1
65 to 69 years	–1.2	2.3	–7.1	–14.9	0.5	–7.9	44.3
70 to 74 years	–3.7	–3.7	–5.3	–2.1	–24.3	–25.1	29.0
75 to 79 years	–1.7	–3.9	19.4	–15.1	–64.3	1.5	–92.3
80 to 84 years	–3.8	–0.2	–1.7	9.0	–28.3	23.4	–4.2
85 years and older	–4.1	3.0	27.4	14.0	36.9	–78.4	0.0

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Population, by Sex and Age Cohorts	Fort Wayne, Indiana	Sterling Heights, Michigan	San Clemente, California	Valparaiso, Indiana	Sunnyside, Washington	Rayne, Louisiana	Ely, Nevada
Summary of 5-Year Cohorts
Maximum	13.6	15.5	27.4	25.5	61.7	72.9	50.7
Minimum	–18.5	–13.7	–19.5	–54.6	–78.4	–78.4	–95.1
Mean absolute difference	3.1	4.7	10.9	10.3	25.9	23.8	30.0