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

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

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Suggested Citation: "Appendix A: Usability Analysis: Tract-Level 2008-2012 ACS Data." 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 A

Usability Analysis: Tract-Level 2008-2012 ACS Data

This appendix presents an expanded version of Table 2-2 (in Chapter 2), providing a detailed overview of the precision and usability of five key American Community Survey variables: (1) persons living in poverty, (2) occupied housing units that are renter occupied, (3) households receiving benefits from the Supplemental Nutrition Assistance Program (SNAP) in the past 12 months, (4) persons who are foreign born, and (5) the population aged 25 and older with a graduate or professional degree.

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TABLE A-1 Usability Analysis: Tract-Level 2008-2012 ACS Data (in percentage)

Characteristics	Percentage of Persons Living in Poverty^a	Percentage of Occupied Housing Units That Are Renter Occupied^b	Percentage of Households Receiving SNAP Benefits in Past 12 Months^c	Percentage of Persons Who Are Foreign Born	Percentage of Population Aged 25+ with a Graduate or Professional Degree^d
National Estimate	14.9	34.5	11.4	12.9	10.6
National Margin of Error	±0.1	±0.2	±0.1	±0.1	±0.1
All Tracts^e
Tract range	0-100	0-100	0-100	0-100	0-100
Tract mean	16.0	35.2	12.5	12.2	10.3
Tract median	12.6	29.8	9.2	6.9	7.2
Tract median CV	28.3	14.7	29.5	29.7	26.0
Tract median MoE	5.8	6.7	4.6	3.4	3.2
CV ≤ 30%	56	88	51	50	61
CV > 30 and ≤ 50%	35	9	29	29	27
CV > 50%	9	2	20	21	12
Confidence interval ≥ 10 percentage points	59	80	45	30	17
MoE > estimate	4	1	16	15	8
Confidence interval lower bound < 0	4	1	16	15	8
Confidence interval upper bound > 100	0.17 (125 tracts)	1.4 (1034 tracts)	0.1 (89 tracts)	0.05 (37 tracts)	0.1 (64 tracts)

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Excluding Tracts Where CV = 0	Percentage of Persons Living in Poverty^f	Percentage of Occupied Housing Units That Are Renter Occupied^g	Percentage of Households Receiving SNAP Benefits in Past 12 Months^h	Percentage of Persons Who Are Foreign Bornⁱ	Percentage of Population Aged 25+ with a Graduate or Professional Degree^j
Tract range	0.02-96.3	0.14-99.8	0.04-94.2	0.02-95.0	0.02-97.4
Tract mean	16.0	34.9	12.9	12.5	10.4
Tract median	12.6	29.7	9.7	7.2	7.3
Tract median CV	28.4	14.8	30.3	30.4	26.2
Tract median MoE	5.8	6.7	4.8	3.5	3.2
CV ≤ 30%	55	88	49	49	60
CV > 30 and ≤ 50%	35	9	30	30	27
CV > 50%	9	2	20	21	13
Confidence interval ≥ 10 percentage points	59	80	46	31	17
MoE > estimate	4	1	13	13	7
Confidence interval lower bound < 0	4	1	13	13	7
Confidence interval upper bound > 100	0.11 (78 tracts)	0.8 (541 tracts)	0.01 (10 tracts)	0.02 (11 tracts)	.03 (19 tracts)

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Characteristics	Percentage of Persons Living in Poverty^a	Percentage of Occupied Housing Units That Are Renter Occupied^b	Percentage of Households Receiving SNAP Benefits in Past 12 Months^c	Percentage of Persons Who Are Foreign Born	Percentage of Population Aged 25+ with a Graduate or Professional Degree^d
Confidence Interval Width ≥ 10 Percentage Points by CV Category, Excluding Tracts Where CV = 0
CV ≤ 30%	73	84	69	48	24
CV > 30 and ≤ 50%	46	58	33	19	9
CV > 50%	30	32	11	8	6
Median CVs by Tract Total Population Size
All Tracts
< 1,000	31.3	18.7	27.2	43.6	37.6
1,000-2,999	29.0	16.0	29.6	38.6	31.4
3,000-4,999	28.1	14.3	29.3	29.6	25.9
5,000-6,999	28.2	14.1	29.8	25.2	23.5
7,000+	27.8	14.4	29.5	20.7	20.8
Excluding Tracts Where CV = 0
< 1,000	37.2	24.6	40.7	54.7	49.4

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1,000-2,999	29.1	16.2	30.6	40.2	31.9
3,000-4,999	28.1	14.4	30.0	30.1	26.0
5,000-6,999	28.2	14.1	30.4	25.3	23.6
7,000+	27.8	14.4	29.9	20.8	20.8
Median CV by Tract Number of Housing Units
All Tracts
≤ 400	32.6	12.0	23.7	29.8	42.9
401-1,000	31.6	18.0	31.8	34.1	35.5
1,001-2,000	28.4	14.9	29.2	30.9	27.4
2,001-4,000	27.4	13.6	29.1	28.1	22.7
4,001-6,000	27.2	13.4	31.8	20.8	17.0
6,001+	26.4	13.7	40.4	16.0	14.2
Excluding Tracts Where CV = 0
≤ 400	48.6	28.9	63.1	35.6	58.5
401-1,000	31.7	18.3	33.2	36.2	36.5
1,001-2,000	28.4	15.0	29.9	31.5	27.5
2,001-4,000	27.4	13.6	29.6	28.3	22.7
4,001-6,000	27.2	13.4	32.4	20.8	17.0
6,001+	26.4	13.7	40.7	16.0	14.2

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Characteristics	Percentage of Persons Living in Poverty^a	Percentage of Occupied Housing Units That Are Renter Occupied^b	Percentage of Households Receiving SNAP Benefits in Past 12 Months^c	Percentage of Persons Who Are Foreign Born	Percentage of Population Aged 25+ with a Graduate or Professional Degree^d
Confidence Interval ≥ 10 Percentage Points by Tract Population Size, Excluding Tracts Where CV = 0
< 1,000	83	93	79	58	61
1,000-2,999	68	86	60	34	28
3,000-4,999	59	80	46	32	16
5,000-6,999	54	77	38	28	11
7,000+	46	67	29	23	6
Confidence Interval ≥ 10 Percentage Points by Tract Number of Housing Units, Excluding Tracts Where CV = 0
≤ 400	88	95	85	45	56
401-1,000	72	88	66	43	30
1,001-2,000	61	81	49	32	17
2,001-4,000	53	77	36	25	13

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4,001-6,000	38	63	16	17	14
6,001+	25	54	10	15	16
MoE > Estimate by Tract Population Size, Excluding Tracts Where CV = 0
< 1,000	25	14	34	43	39
1,000-2,999	6	2	14	22	13
3,000-4,999	4	1	12	11	6
5,000-6,999	3	0.5	12	7	3
7,000+	2	0.4	10	3	2
MoE > Estimate by Tract Number of Housing Units, Excluding Tracts Where CV = 0
≤ 400	36	20	52	22	47
401-1,000	9	3	17	22	19
1,001-2,000	4	1	13	14	7
2,001-4,000	2	0.3	11	8	2
4,001-6,000	1	0	12	1	0.2

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Characteristics	Percentage of Persons Living in Poverty^a		Percentage of Occupied Housing Units That Are Renter Occupied^b		Percentage of Households Receiving SNAP Benefits in Past 12 Months^c		Percentage of Persons Who Are Foreign Born		Percentage of Population Aged 25+ with a Graduate or Professional Degree^d
6,001+	1		0		13		2		0

^aTracts with no persons in the universe for which poverty rates are calculated were excluded from this analysis.

^bTracts with no households were excluded from this analysis.

^cSNAP is Supplemental Nutrition Assistance Program; tracts with no households were excluded from this analysis.

^dTracts with no persons aged 25 and older were excluded from this analysis.

^eTracts with zero population are excluded.

^fThere are 265 tracts excluded because the estimated poverty rate equals zero. When the poverty rate is zero, the CV cannot be calculated and is set to zero.

^gThere are 596 tracts excluded because either the standard error of the percentage of renter-occupied households equals zero or the percentage of renter-occupied households equals zero. When the percentage renter occupied is zero, the CV cannot be calculated and is set to zero.

^hThere are 2,754 tracts excluded because either the standard error of the percentage with SNAP benefits equals zero or the percentage with SNAP benefits equals zero. When the percentage with SNAP benefits is zero, the CV cannot be calculated and is set to zero.

ⁱThere are 1,806 tracts excluded because either the standard error of the percentage of the foreign-born population equals zero or the percentage of the foreign–born population equals zero. When the percentage population is zero, the CV cannot be calculated and is set to zero.

^jThere are 940 tracts excluded because either the standard error of the percentage of persons with a professional degree equals zero or the percentage of persons with a professional degree equals zero. When the percentage with a professional degree is zero, the CV cannot be calculated and is set to zero.

NOTE: MoE is margin of error; CV is coefficient of variation.

SOURCE: Panel analysis of data from the 2008-2012 ACS Summary File, available at http://www.census.gov/acs/www/data_documentation/summary_file/ [September 2014].