Geographic Aggregation Error: City-Level Summary

Average accuracy across all wards and districts

This page summarizes block-level geographic aggregation error across all wards and districts for each supported city. The tables below isolate the error caused purely by geographic boundary mismatch — independent of sampling or time differences between ACS and Census. All estimates come from 2020 decennial census block data aggregated to tracts or block groups, then re-estimated for each ward or district.

Block-Level Geographic Aggregation Error

The tables below isolate the error caused purely by geographic boundary mismatch — independent of sampling or time differences between ACS and Census. All estimates come from 2020 decennial census block data aggregated to tracts or block groups, then re-estimated for each ward or district. For each city, errors are averaged across all wards/districts.

Cross-City Comparison

Variable
Chicago (50 wards)
New York City (51)
Los Angeles (15)
Hybrid Tract Hybrid Tract Hybrid Tract
Race
Hispanic or Latino 0.28 pp 0.52 pp 0.08 pp 0.23 pp 0.08 pp 0.12 pp
White 0.27 pp 0.46 pp 0.08 pp 0.27 pp 0.08 pp 0.12 pp
Black 0.45 pp 0.75 pp 0.05 pp 0.16 pp 0.02 pp 0.04 pp
Asian 0.10 pp 0.16 pp 0.09 pp 0.21 pp 0.03 pp 0.06 pp
Other or Multi-racial 0.03 pp 0.04 pp 0.02 pp 0.03 pp 0.01 pp 0.02 pp
Average Absolute Error 0.23 pp 0.38 pp 0.06 pp 0.18 pp 0.04 pp 0.07 pp
Age Group
Under 5 years 0.05 pp 0.07 pp 0.02 pp 0.03 pp 0.01 pp 0.01 pp
5 to 17 years 0.11 pp 0.19 pp 0.03 pp 0.06 pp 0.02 pp 0.03 pp
18 to 24 years 0.20 pp 0.27 pp 0.02 pp 0.04 pp 0.01 pp 0.02 pp
25 to 44 years 0.28 pp 0.39 pp 0.04 pp 0.10 pp 0.03 pp 0.05 pp
45 to 64 years 0.15 pp 0.21 pp 0.04 pp 0.06 pp 0.02 pp 0.03 pp
65 years and over 0.16 pp 0.26 pp 0.05 pp 0.10 pp 0.02 pp 0.02 pp
Average Absolute Error 0.16 pp 0.23 pp 0.03 pp 0.07 pp 0.02 pp 0.02 pp
Housing Tenure
Owner-occupied 0.50 pp 0.71 pp 0.10 pp 0.27 pp 0.09 pp 0.08 pp
Renter-occupied 0.50 pp 0.71 pp 0.10 pp 0.27 pp 0.09 pp 0.08 pp
Average Absolute Error 0.50 pp 0.71 pp 0.10 pp 0.27 pp 0.09 pp 0.08 pp
Housing Occupancy
Occupied Housing 0.13 pp 0.16 pp 0.04 pp 0.09 pp 0.05 pp 0.05 pp
Vacant Housing 0.13 pp 0.16 pp 0.04 pp 0.09 pp 0.05 pp 0.05 pp
Average Absolute Error 0.13 pp 0.16 pp 0.04 pp 0.09 pp 0.05 pp 0.05 pp
Household Size
1-person HH 0.27 pp 0.43 pp 0.07 pp 0.14 pp 0.05 pp 0.08 pp
2-person HH 0.19 pp 0.25 pp 0.05 pp 0.07 pp 0.03 pp 0.04 pp
3-person HH 0.09 pp 0.14 pp 0.04 pp 0.06 pp 0.04 pp 0.05 pp
4+ person HH 0.12 pp 0.24 pp 0.05 pp 0.10 pp 0.05 pp 0.07 pp
Average Absolute Error 0.17 pp 0.26 pp 0.05 pp 0.09 pp 0.04 pp 0.06 pp
Household Type
Family Households 0.27 pp 0.39 pp 0.07 pp 0.14 pp 0.06 pp 0.09 pp
Married-couple Family 0.25 pp 0.38 pp 0.06 pp 0.13 pp 0.06 pp 0.09 pp
Non-family Households 0.27 pp 0.39 pp 0.07 pp 0.14 pp 0.06 pp 0.09 pp
Living Alone 0.27 pp 0.43 pp 0.07 pp 0.14 pp 0.05 pp 0.08 pp
Average Absolute Error 0.27 pp 0.40 pp 0.06 pp 0.14 pp 0.06 pp 0.09 pp
Overall Average Absolute Error 0.22 pp 0.34 pp 0.05 pp 0.13 pp 0.04 pp 0.06 pp
All errors from 2020 decennial census block data. Errors averaged across all wards/districts in each city.

Chicago (50 wards)

Variable
Tract Error
Hybrid Error
Avg Max Avg Max
Race
Hispanic or Latino 0.52 pp 2.53 pp 0.28 pp 1.65 pp
White 0.46 pp 4.91 pp 0.27 pp 3.56 pp
Black 0.75 pp 5.26 pp 0.45 pp 3.92 pp
Asian 0.16 pp 0.71 pp 0.10 pp 0.47 pp
Other or Multi-racial 0.04 pp 0.14 pp 0.03 pp 0.12 pp
Average Absolute Error 0.38 pp 5.26 pp 0.23 pp 3.92 pp
Age Group
Under 5 years 0.07 pp 0.27 pp 0.05 pp 0.15 pp
5 to 17 years 0.19 pp 0.83 pp 0.11 pp 0.59 pp
18 to 24 years 0.27 pp 2.18 pp 0.20 pp 1.93 pp
25 to 44 years 0.39 pp 2.79 pp 0.28 pp 2.28 pp
45 to 64 years 0.21 pp 1.38 pp 0.15 pp 0.85 pp
65 years and over 0.26 pp 1.39 pp 0.16 pp 0.96 pp
Average Absolute Error 0.23 pp 2.79 pp 0.16 pp 2.28 pp
Housing Tenure
Owner-occupied 0.71 pp 2.96 pp 0.50 pp 2.04 pp
Renter-occupied 0.71 pp 2.96 pp 0.50 pp 2.04 pp
Average Absolute Error 0.71 pp 2.96 pp 0.50 pp 2.04 pp
Housing Occupancy
Occupied Housing 0.16 pp 1.02 pp 0.13 pp 0.51 pp
Vacant Housing 0.16 pp 1.02 pp 0.13 pp 0.51 pp
Average Absolute Error 0.16 pp 1.02 pp 0.13 pp 0.51 pp
Household Size
1-person HH 0.43 pp 1.64 pp 0.27 pp 1.14 pp
2-person HH 0.25 pp 1.55 pp 0.19 pp 0.85 pp
3-person HH 0.14 pp 0.74 pp 0.09 pp 0.44 pp
4+ person HH 0.24 pp 1.07 pp 0.12 pp 0.32 pp
Average Absolute Error 0.26 pp 1.64 pp 0.17 pp 1.14 pp
Household Type
Family Households 0.39 pp 1.39 pp 0.27 pp 0.95 pp
Married-couple Family 0.38 pp 1.52 pp 0.25 pp 0.98 pp
Non-family Households 0.39 pp 1.39 pp 0.27 pp 0.95 pp
Living Alone 0.43 pp 1.64 pp 0.27 pp 1.14 pp
Average Absolute Error 0.40 pp 1.64 pp 0.27 pp 1.14 pp
Average Absolute Error Across Categories 0.36 pp 5.26 pp 0.24 pp 3.92 pp
Avg/Max computed across all 50 wards using 2020 decennial census block data.
Average Absolute Error Across Categories: simple average of the six category-level averages.

New York City (51 districts)

Variable
Tract Error
Hybrid Error
Avg Max Avg Max
Race
Hispanic or Latino 0.23 pp 1.22 pp 0.08 pp 0.43 pp
White 0.27 pp 1.22 pp 0.08 pp 0.38 pp
Black 0.16 pp 0.71 pp 0.05 pp 0.21 pp
Asian 0.21 pp 2.08 pp 0.09 pp 0.61 pp
Other or Multi-racial 0.03 pp 0.13 pp 0.02 pp 0.07 pp
Average Absolute Error 0.18 pp 2.08 pp 0.06 pp 0.61 pp
Age Group
Under 5 years 0.03 pp 0.18 pp 0.02 pp 0.06 pp
5 to 17 years 0.06 pp 0.20 pp 0.03 pp 0.09 pp
18 to 24 years 0.04 pp 0.18 pp 0.02 pp 0.15 pp
25 to 44 years 0.10 pp 0.54 pp 0.04 pp 0.11 pp
45 to 64 years 0.06 pp 0.30 pp 0.04 pp 0.13 pp
65 years and over 0.10 pp 0.42 pp 0.05 pp 0.27 pp
Average Absolute Error 0.07 pp 0.54 pp 0.03 pp 0.27 pp
Housing Tenure
Owner-occupied 0.27 pp 1.70 pp 0.10 pp 0.39 pp
Renter-occupied 0.27 pp 1.70 pp 0.10 pp 0.39 pp
Average Absolute Error 0.27 pp 1.70 pp 0.10 pp 0.39 pp
Housing Occupancy
Occupied Housing 0.09 pp 0.47 pp 0.04 pp 0.28 pp
Vacant Housing 0.09 pp 0.47 pp 0.04 pp 0.28 pp
Average Absolute Error 0.09 pp 0.47 pp 0.04 pp 0.28 pp
Household Size
1-person HH 0.14 pp 0.49 pp 0.07 pp 0.22 pp
2-person HH 0.07 pp 0.17 pp 0.05 pp 0.18 pp
3-person HH 0.06 pp 0.23 pp 0.04 pp 0.17 pp
4+ person HH 0.10 pp 0.41 pp 0.05 pp 0.14 pp
Average Absolute Error 0.09 pp 0.49 pp 0.05 pp 0.22 pp
Household Type
Family Households 0.14 pp 0.58 pp 0.07 pp 0.28 pp
Married-couple Family 0.13 pp 0.43 pp 0.06 pp 0.22 pp
Non-family Households 0.14 pp 0.58 pp 0.07 pp 0.28 pp
Living Alone 0.14 pp 0.49 pp 0.07 pp 0.22 pp
Average Absolute Error 0.14 pp 0.58 pp 0.06 pp 0.28 pp
Average Absolute Error Across Categories 0.14 pp 2.08 pp 0.06 pp 0.61 pp
Avg/Max computed across all 51 districts using 2020 decennial census block data.
Average Absolute Error Across Categories: simple average of the six category-level averages.

Los Angeles (15 districts)

Variable
Tract Error
Hybrid Error
Avg Max Avg Max
Race
Hispanic or Latino 0.12 pp 0.56 pp 0.08 pp 0.30 pp
White 0.12 pp 0.30 pp 0.08 pp 0.21 pp
Black 0.04 pp 0.12 pp 0.02 pp 0.07 pp
Asian 0.06 pp 0.23 pp 0.03 pp 0.08 pp
Other or Multi-racial 0.02 pp 0.04 pp 0.01 pp 0.02 pp
Average Absolute Error 0.07 pp 0.56 pp 0.04 pp 0.30 pp
Age Group
Under 5 years 0.01 pp 0.02 pp 0.01 pp 0.02 pp
5 to 17 years 0.03 pp 0.12 pp 0.02 pp 0.06 pp
18 to 24 years 0.02 pp 0.05 pp 0.01 pp 0.05 pp
25 to 44 years 0.05 pp 0.16 pp 0.03 pp 0.08 pp
45 to 64 years 0.03 pp 0.09 pp 0.02 pp 0.05 pp
65 years and over 0.02 pp 0.06 pp 0.02 pp 0.06 pp
Average Absolute Error 0.02 pp 0.16 pp 0.02 pp 0.08 pp
Housing Tenure
Owner-occupied 0.08 pp 0.31 pp 0.09 pp 0.20 pp
Renter-occupied 0.08 pp 0.31 pp 0.09 pp 0.20 pp
Average Absolute Error 0.08 pp 0.31 pp 0.09 pp 0.20 pp
Housing Occupancy
Occupied Housing 0.05 pp 0.19 pp 0.05 pp 0.17 pp
Vacant Housing 0.05 pp 0.19 pp 0.05 pp 0.17 pp
Average Absolute Error 0.05 pp 0.19 pp 0.05 pp 0.17 pp
Household Size
1-person HH 0.08 pp 0.23 pp 0.05 pp 0.19 pp
2-person HH 0.04 pp 0.16 pp 0.03 pp 0.10 pp
3-person HH 0.05 pp 0.17 pp 0.04 pp 0.15 pp
4+ person HH 0.07 pp 0.20 pp 0.05 pp 0.14 pp
Average Absolute Error 0.06 pp 0.23 pp 0.04 pp 0.19 pp
Household Type
Family Households 0.09 pp 0.31 pp 0.06 pp 0.23 pp
Married-couple Family 0.09 pp 0.24 pp 0.06 pp 0.21 pp
Non-family Households 0.09 pp 0.31 pp 0.06 pp 0.23 pp
Living Alone 0.08 pp 0.23 pp 0.05 pp 0.19 pp
Average Absolute Error 0.09 pp 0.31 pp 0.06 pp 0.23 pp
Average Absolute Error Across Categories 0.06 pp 0.56 pp 0.05 pp 0.30 pp
Avg/Max computed across all 15 districts using 2020 decennial census block data.
Average Absolute Error Across Categories: simple average of the six category-level averages.