1. The European Statistical Training Programme (ESTP)

2. Chapter 5: The analysis of nonresponse
Handbook: chapter 5
How to detect a bias?
Where to find auxiliary information
An example: POLS 1998
Global analysis
A more detailed analysis
Conclusions

3. How to detect a bias? The question:
How to detect whether estimates for a target variable are biased if you don’t know its values for the nonrespondents?
The answer:
Use auxiliary variables!
Auxiliary variables:
Have been measured in the survey
Population (or complete sample) distribution is available
Correlated with target variables
Important:
Decision to include auxiliary variables in survey at design stage.

4. How to detect a bias?
Possible relationships between target variable, response behaviour and auxiliary variable
Missing Completely At Random (MCAR):
No relation between X and R. No bias. No problem.
Missing At Random (MAR):
Relation between X and R. Bias can be reduced by using X.
Not Missing At Random (MAR):
Direct relation between Y and R. Bias cannot be reduced.
Response behaviour R
Auxiliary variable X
Target variable Y

5. Where to find auxiliary variables?
In the sampling frame itself
Example: Survey on Household Living Conditions 1998
Two-stage sample, first stage: municipalities, second stage: persons from population register
Auxiliary variables: gender, age, marital status, geographical area

6. Where to find auxiliary variables?
Observations by interviewers
Example: Housing Demand Survey 1977/1978
Estimate of building period of house, Type of house, Number of floors.

7. Where to find auxiliary variables?
National Statistical Institute
Example: Survey on Household Living Conditions 1998
Population by sex, age, marital status and region

8. Survey on Household Living Conditions 1998 (POLS)
Continuous survey
Every month a new sample, thematic modules
Fieldwork
First month CAPI, second month CATI
Fieldwork results
Frequency
Percentage
Sample size
39 302
100.0 %
Response
Immediate response
Converted refusers
Other response
24 008
9718
14 275 15
61.1 %
24.7 %
36.3 %
0.0 %
Nonresponse
Unprocessed cases
Non contact (not-at-home)
Non contact (moved)
Not able (illness, handicap)
Not able (language problem)
Refusal
Other nonresponse
15 294
2 514
2 093
376
735
416
8 918
242
38.9 %
6.4 %
5.3 %
1.0 %
1.9 %
1.1 %
22.7 %
0.6 %

9. Survey on Household Living Conditions 1998 (POLS)
Composition of nonresponse

10. Survey on Household Living Conditions 1998 (POLS)
Auxiliary variables
Social Statistics Database of Statistics Netherlands
Data on demography, geography, income, labour, education, health, social protection
Variables used: sex, age, province, ethnic group, employment, social security benefits
Data on postal code areas
420,000 area’s, homogeneous with respect to socio-economic characteristics
Variables used: urbanisation, town size, percentage non-natives, average housing value
Fieldwork data
Information about all contact attempts
Variables used: result of contact attempt, type of nonresponse, interviewer district, telephone number

11. Global nonresponse analysis of POLS 1998
Age

12. Global nonresponse analysis of POLS 1998
Marital status

13. Global nonresponse analysis of POLS 1998
Household size

14. Global nonresponse analysis of POLS 1998
Degree of urbanisation

15. Global nonresponse analysis of POLS 1998
Province

16. Global nonresponse analysis of POLS 1998
Average house value in neighbourhood

17. Global nonresponse analysis of POLS 1998
Percentage of non-natives in neighbourhood

18. Global nonresponse analysis of POLS 1998
Listed fixed-line telephone number

19. Detailed analysis Ingredients for a detailed analysis of nonresponse
Respondent characteristics
Neighbourhood characteristics
Interviewer and data collection characteristics

20. Detailed analysis Respondent characteristics
Demographics like age, gender, marital status, type of household
Socio-economics like income, employment, education
Neighbourhood characteristics
Type of dwelling and neighbourhood, degree of urbanisation
Interviewer and data collection characteristics
Type of nonresponse
Contact and refusal strategy
Interviewer experience and gender
Interview mode

21. Detailed analysis Decomposition of response process Sample Processed?
Not processed
Not moved?
Moved
Contacted?
Not contacted
Participated?
Language problem
Not able
Refusal
Response

22. Detailed analysis Why a decomposition of the response process?
It gives insight into the possible causes for selective response
It may reveal possible measures to reduce nonresponse
It enables the incorporation of auxiliary information
Compare survey topics to steps in response process
Do you travel a lot?
Did you recently buy a new house?
How many years of education in Dutch do you have?
Do you participate in surveys?

23. Detailed analysis Processing allocated cases
Respondent characteristics: listed phone, access to web
Neighbourhood characteristics: type of neighbourhood
Interviewer and data collection characteristics: interviewer workload
Example
Interviewer district, average value of houses
Proportion explained: 9.1%

24. Detailed analysis Processing allocated cases
Respondent characteristics: listed phone, access to web
Neighbourhood characteristics: type of neighbourhood
Interviewer and data collection characteristics: interviewer workload
Example
Interviewer district, average value of houses
Proportion explained: 9.1%

25. Detailed analysis Non-contacted cases
Respondent characteristics: available auxiliary information
Neighbourhood characteristics: available auxiliary information
Interviewer and data collection characteristics: number and timing of contact attempts, registered phone, interviewer workload
Example
Registered phone, interviewer district, age, type of household
Proportion explained: 15.2%

26. Detailed analysis Non-contacted cases N=32996P= 5.9% N=25512 P=3.8%
Listed phone number
No listed phone number
Other
Child, married, single parent, partner in unmarried couple without children
Other towns
Big cities
Flevoland,
Amsterdam
N=232
P=8.2%
N=1494
P=18.9%
Divorced
N=482
P=13.3%
N=1012
P=21.5%
N=1064
P=30.3%
N=581
P=17.2%
Districts: 8,12,15,17
Couple without children, single parent
Districts
Detailed analysis
Non-contacted cases

27. Detailed analysis Language problems
Respondent characteristics: available auxiliary information
Neighbourhood characteristics: available auxiliary information
Interviewer and data collection characteristics: ethnicity of interviewer, proxy-interviewing
Example
Ethnicity, i.e. origin and generation
Proportion explained: 51.2%

28. Detailed analysis Mentally or physically not able
Respondent characteristics: available auxiliary information
Neighbourhood characteristics: available auxiliary information
Interviewer and data collection characteristics: -
Example
Age, employment status
Proportion explained: 20%

29. Detailed analysis Refusals
Respondent characteristics: available auxiliary information
Neighbourhood characteristics: available auxiliary information
Interviewer and data collection characteristics: interviewer experience, interviewer gender and age, interview mode, follow up strategy
Example
Registered phone, type of household, average house value, age, interviewer district
Proportion explained: <5%

30. Detailed analysis In summary, literature confirms most findings
Sample
Processed?
Interviewer workload,
average house value
Not moved?
Age,type of household,
Contacted?
Registered phone, interviewer
workload, age, type of household
Participated?
Age, interviewer experience,ethnic
background, interviewer experience,
average house value
Response

31. Conclusions Identify and link available auxiliary information
Respondent characteristics
Neighbourhood characteristics
Interviewer and data collection characteristics
Investigate literature on similar surveys and data collection strategies
If not available plan future collection of missing crucial auxiliary information
Decompose response process
Make at least a distinction between contact and participation
Relate survey topics to steps in response process
Relate interviewer and data collection characteristics to steps in response process
Identify mode characteristics