1. A Review of the Address Coverage Enhancement Scheme for In-person Household Surveys
Michael Jones, Westat
Sylvia Dohrmann, Graham Kalton, Jean Opsomer, Westat
JSM 2019 • Denver, Colorado • July 27-August 1
The views presented in this paper are those of the author(s) and do not represent
the views of any Government Agency/Department or Westat

2. The Three Steps of the ACE Procedure
Step 1: Select area segments for ACE
Probabilities of selection
Step 2: Field work in ACE segments
Canvas the segments
Step 3: Verify addresses added in the field through ACE
In-house review of addresses
Vendor comparison of addresses to the CDS

3. Illustrative Example – Area Segment vs List Segment

4. Illustrative Example – Area Segment vs List Segment
Illustration of ACE
Area Segment
List Segment

5. Step 1: Select ACE Segments
ACE is performed in a subsample of the study’s area segments
Let P(i) = P(area segment i is selected for ACE) = kiri ,
Where 1/ki = P(selecting ACE added address j if area segment i is selected)
And ri = the within segment sampling rate for list segment i
ki can be adjusted depending on the estimated CDS coverage and to control workload

6. Step 1: Select ACE Segments – Adjusting Probabilities of Selection
ki > 1 if CDS coverage is expected to be low
E.g., set ki = 3 then P(i) = 3ri
if the number of ACE added addresses is 30, we sample 10
ki < 1 if CDS coverage is expected to be high
E.g., set ki = 0.75 then P(i) = 0.75ri
if the number of ACE added addresses is 3, take all and adjust weights by a factor of 1.333
ki = 1/ri if CDS coverage is expected to be LOW
P(i) = 1 and the within segment sampling rate is ri

7. Step 1: Select ACE Segments – Indicators of Coverage & Improving Probabilities
Comparison of segment-level census count and CDS count
If census count is much larger, can indicate poor coverage
Urbanicity of segments
Coverage generally better in urban areas
Improving the probabilities of selection for ACE segments
How to best define urbanicity?
Could some segments with expected good coverage be assigned a zero chance of inclusion for ACE?

8. Step 2: Field Work – The Canvas
Field workers canvas the area segments
List segment addresses are provided on a tablet
Compare the addresses inside the area segment to the addresses on the tablet, i.e., to the list segment
Addresses not in the list segment are added to the tablet
Transfer the added addresses back to the home office

9. Step 2: Field Work – Timing
ACE field work can be done before or during the data collection period
Preference is to perform it before
Avoids conflicts with data collection if interviewers perform ACE
Allows for coordinated sampling of ACE and CDS addresses
If conducted by interviewers during the data collection period
Better for interviewers to complete ACE before interviewing CDS cases

10. Illustrative Example – No Geocoding Error
Illustration of ACE
Area Segment
List Segment
Located and geocoded inside area segment
Located inside area segment, not on CDS

11. Illustrative Example – Geocoding Error
Illustration of ACE
Area Segment
List Segment
Located outside area segment, geocoded into the area segment
Located and geocoded inside area segment
Located inside area segment, on CDS
Located inside area segment, not on CDS

12. Step 2: Field Work – Geocoding Error
Enhancement procedures treat geocoding differently
How enhancement procedures handle geocoding error
Type of Geocoding Error
ACE
EL & CHUM
Address located outside the area segment, geocoded inside
Retained on frame
Removed from frame
Address located inside the area segment, geocoded outside
Not added to frame
Added to frame

13. Step 2: Field Work – Geocoding Error
The level of geocoding error depends on the geocoding methodology
Most implementations of ACE have used our vendor’s geocoding
Street address interpolation is the most precise
Interpolates a position along a street section based on the street addresses
More recently, we have used in-house land parcel geocoding
Geocoordinates on the address property is the most precise
Street address interpolation is the next level
Therefore, at least as accurate as the vendor’s method

14. Step 2: Field Work – Geocoding Error
As part of ACE, the field workers record whether the list segment addresses were located within or outside the segment.
The percentage of CDS addresses in the list segments correctly geocoded into the area segments
Vendor street address interpolation
Westat land parcel geocoding
Urban segments
93%
97%
Rural segments
78%
92%
Overall
91%
96%

15. Step 2: Field Work – Geocoding Error
The greater the amount of geocoding error,
The more addresses added by ACE that need to be resolved
The more addresses sampled from the list segment that are located outside the area segment
Percentage of addresses added in ACE field work that geocoded to another area segment
Vendor street address interpolation
Westat land parcel geocoding
Urban segments
68%
47%
Rural segments
37%
20%
Overall
52%
32%

16. Illustrative Example – Canvassing Complete
Illustration of ACE
Area Segment
List Segment
Located outside area segment, geocoded into the area segment
Located and geocoded inside area segment
Located inside area segment, not on the field-worker’s list

17. Illustrative Example – Differentiating Address Types
Illustration of ACE
Area Segment
List Segment
Located outside area segment, geocoded into the area segment
Located and geocoded inside area segment
Located through ACE, on CDS
Located through ACE, not on CDS

18. Step 3: Verification of Addresses Added in the Field
Compare 2nd
review
addresses
to to CDS
Field
Worker
Review
addresses
not on CDS
Vendor
Indicate addresses not on CDS
Initial review
of all added
addresses
Compare
added addresses
to CDS
Canvas ACE segment and enter addresses not on tablet
Addresses not on CDS are added to create an ACE enhanced frame and are ready to be sampled

19. Step 3: Streamlining Verification of Addresses Added in the Field
Consider eliminating the second review
Of the ACE added addresses determined to be on the CDS, 95% are identified during the first vendor comparison
Do not review all ACE added addresses
Instead, select the sample of ACE added addresses after canvassing
Verify the address during the screener interview
Send the verified addresses to the vendor to determine which are on the CDS
If address is on the CDS, adjust the weight by one-half

20. Illustrative Example – Select the Sample
Illustration of ACE
Area Segment
List Segment
Located outside area segment, geocoded into the area segment
Located and geocoded inside area segment
Located through ACE, on CDS
Located through ACE, not on CDS
Sampled

21. Summary
Benefits of the ACE procedure include
Only a sample of segments undergo the procedure, but provides full coverage
Is a separate procedure from data collection, i.e., timing is flexible
Retains all CDS addresses geocoded to the area segments
Areas for further research
Improve methods for identifying areas with high numbers of addresses not on the CDS file
Improve the method for checking addresses against the CDS
Consider benefits of accepting some addresses on the CDS and halving their weights

22. Thank you!
Questions can be directed to: