1. Non-Response Bias in Income Data
Mari Toomse
University of Essex

2. Research topic Non-response bias in annual income measures:
Sources and mechanism of bias
Predicting bias from survey data
Relationship with measurement error
Cumulative bias in a panel study

3. Data
Estonian EU-SILC 2007 (Statistics on Income and Living Conditions)
Panel study on income
Comes with call record data
Linked on individual level to Tax and Customs Board register
Respondents AND
Non-respondent

4. Research design I Non-response bias – variable specific
Response process as a sequence of events
Case issued
Address known
Contact achieved
Co-operation achieved
Item response

5. Research design II Mechanisms causing these events are different
Assess the net effect of each processes
Annual salary data from the regiser
Linked to the outcome of the whole of the selected sample
New cases
Panel cases

6. Mean salary

7. Probability of contact, 1st year
Model 1 Model 2 Model 3
Intercept ** ** **
Salary **
Type of settlement
Rural
Area
Northern ** **
Western
Central **
Northeastern
Gender
Male
Age **

8. Probability of item response, 1st year
Model 1 Model 2 Model 3
Intercept ** ** **
Salary ** ** **
Type of settlement
Rural
Area
Northern
Western
Central
Northeastern
Gender
Male
Age

9. Quintile distribution, 1st year

10. Conclusions
There is a substantial negative net bias in annual salary estimates
Bias accumulates over the course of a panel
Main sources of bias are non-contact and item non-response
Bias due to non-contact is largerly explained away by basic grographical variables

11. Thank you for your attention!