1. EU-SILC Tracing Rules Implementation: Pros and Cons
Workshop on Best Practices for EU-SILC revision
Warsaw, October 2018
EU-SILC Tracing Rules Implementation:
Pros and Cons
Lucia Coppola, Daniela Lo Castro, Mattia Spaziani
ISTAT

2. Tracing Rules
Longitudinal component to estimate changes in economic conditions and determinants.
Tracing rules (TR) define which units have to be followed up and interviewed, i.e. the units representative of the target population.
TR contribute to define the longitudinal population and both cross-sectional and longitudinal sample size and representativeness.
Complex TR may contribute to achieve a higher sample dimension and a better representativeness of sub-populations (e.g. new households, households with high mobility etc.).
Complex TR may be very demanding for both respondents and NSI, and may not be successfully implemented (e.g. units to be followed are not likely to be interviewed, and sub-populations are not properly represented in the sample)
A wide debate on EU-SILC Tracing Rules in the Future (i.e. IESS and implementing regulation).
=> some empirical evidence to discuss Pros and Cons and keep the debate open

3. SAMPLE INDIVIDUALS & CORESIDENTS
EU-SILC TR are defined at individual level.
Sample Individuals have to be traced and followed in the national territory & the family they belong to at the moment of the data collection is defined as Sample Household
Any household member aged 14+ at first wave is defined as a SAMPLE INDIVIDUAL (if the panel duration is 4 years…. lower otherwise => 'sample persons' means members of the household in the initial sample aged at least 16 years minus half of duration of a panel (if applicable rounded upwards)).
A household member aged less than 14 at first wave and any individual who becomes a household member from the second wave onwards is defined as CORESIDENT.
Coresidents are not traced and followed, unless they move with a sample individual.

4. SAMPLE INDIVIDUALS & CORESIDENTS
A SAMPLE individual quits the panel if he/she does not belong any longer to the target population (i.e. he/she dies, moves abroad or to an institution).
Otherwise, if a sample individual leaves the original household (i.e. first wave household) to form a new household, the latter is defined as SPLIT-OFF household and belongs to the sample for the whole panel duration.
SAMPLE HOUSEHOLDS have to be interviewed during the whole panel duration, unless:
- Non-contacted the first year of the panel
- Non-enumerated a single year due to the impossibility of locating the address, the address being non-residential or unoccupied, lost (no information on what happened to the household), or the household refusing to co-operate
- Non-contacted two consecutive years due to the impossibility of accessing the address, because the whole household is temporarily away or is unable to respond due to incapacity or illness or for other serious reasons

5. Under DISCUSSION Minimum age to be a Sample Person
The role of SPLIT-OFF households
When to re-contact a sample household
DATA =>
UDB, longitudinal release
26 countries
4 years panel only

6. SAMPLE PERSONS & CORESIDENTS
First wave sample
Second wave sample
HH members aged 14+
Sample persons
HH members aged 14+ at first wave and still in scope
Sample persons
HH members aged <14
Coresidents
HH members aged <14 at first wave and still living with a SP
Coresidents
New HH members
Coresidents

7. SAMPLE PERSONS & CORESIDENTS
First wave sample
Second wave sample
HH members aged 14+
Sample persons
HH members aged 14+ at first wave and still in scope
Sample persons
Non-zero longitudinal weight
Non-zero longitudinal weight
HH members aged <14
Coresidents
HH members aged <14 at first wave and still living with a SP
Coresidents
Zero longitudinal weight
New HH members
Coresidents

8. SAMPLE PERSONS & CORESIDENTS
First wave sample
Second wave sample
What if the minimum age is increased to 16
(i.e. age at eligibility for individual interview)?
If individuals aged at first interview are defined as coresidents
and they live with another sample person => they stay in the panel
and they do not live with another sample person => they quit the panel
HH members aged 14+
Sample persons
HH members aged 14+ at first wave and still in scope
Sample persons
Non-eligible for individual interview
SP aged 14-15
HH members aged <14
Coresidents
HH members aged <14 at first wave and still living with a SP
Coresidents
Zero longitudinal weight
New HH members
Coresidents

9. HH with SP aged<16 at first wave
SAMPLE PERSONS & CORESIDENTS
Sample Households where all the sample persons are aged <16 at first wave, by country and year
Country
Year
HH with SP aged<16 at first wave
Total HH % BE
2015 1
1528
0.07
2016
1438 BG
3141
0.03 EE
1371
1361 ES
2813
0.04
2621 FR
2013 2
8733
0.02
2014 3
7913 4
7011
0.06 7
6161
0.11 HU
1764 IT
4167 PL
2766
What if the minimum age is increased to 16
(i.e. age at eligibility for individual interview)?
In the longitudinal UDB ,
taking into account the full panel (4 years) only 26 households
in 10 countries
(out of 25 countries considered in the analyses) would be lost.
Similar results in previous UDB

10. The role of SPLIT-OFF households
Sample Persons who leave the family of origin (first wave) to live in another private household in the national territory form a so called SPLIT-OFF Household
This is a sample household and belongs to the longitudinal and cross-sectional sample
How successful is the follow up of sample individuals who moves?
How many SPLIT-OFF households are in longitudinal sample?

11. The role of SPLIT-OFF households
First Wave
Second Wave
Sample persons
Same household Wave 1
Potential Split-off Households, but some are not successfully followed (e.g. no enough information to locate the new household or refuse to cooperate, etc.)
Interviewed
SPLIT-OFF HH
Moved to another private household
Non-Interviewed
Out of scope
Non-interviewed household

12. The role of SPLIT-OFF households
First Wave
Second Wave
Distribution of sample persons at second wave, by household membership status
Sample persons
Only 1.6% of sample individuals move to another private household:
i.e. a potential SPLIT-OFF household
Same household Wave 1
Moved to another private household
Out of scope
Non-interviewed household
UDB
19 selected countries, with split-off households
4 years panel only

13. The role of SPLIT-OFF households
First Wave
Second Wave
Sample persons
Only 1.6% of sample individuals move to another private household:
i.e. a potential SPLIT-OFF household
Same household Wave 1
Distribution of sample persons who moves, by household membership status
Moved to another private household
But only 0.6% of sample individuals move to another private household which is actually interviewed:
i.e. a SPLIT-OFF household
Out of scope
Non-interviewed household
UDB
19 selected countries, with split-off households
4 years panel only

14. i.e. a SPLIT-OFF household
The role of SPLIT-OFF households
First Wave
Following Waves
During the whole panel (i.e. 2°, 3° and 4° wave), several experiences may occur.
We consider (hierarchically) the sample person is :
interviewed at least once in a split-off HH
no longer interviewed because becomes out of scope
no longer interviewed for other reasons
interviewed only in the same household as 1° wave
Sample persons
About 13% of sample individuals are not in interviewed households after 1° wave, although they were supposed to be followed => weights have to compensate for their attrition….
During the next 3 years, only 1.1% of sample individuals move to another private household which is actually interviewed at least once
i.e. a SPLIT-OFF household
UDB
19 selected countries, with split-off households
4 years panel only

15. The role of SPLIT-OFF households
Distribution of Split-Off Households,
Total Households and incidence of Split-Off Households by year, in 18/26 countries with SPLIT
Distribution of Split-Off Households, Total Households and incidence of Split-Off Households by country, last year
The incidence of Split-Off HH in the last year of the panel is heterogeneous, and higher than 3% in 8 countries.
The sample size in one single panel may be low, but since the incidence is quite high, estimates may be achieved by pooling different panels.
Split-Off HH may contribute to both longitudinal and cross-sectional estimates.
COUNTRY
YEAR
SPLIT HH
TOT HH % AT
2016 49
1203
4.07 BE 71
1438
4.94 BG 26
3141
0.83 CH 68
1533
4.44 CY 33
823
4.01 CZ 20
1765
1.13 EE 59
1361
4.34 EL 30
2131
1.41 ES 98
2621
3.74 HR 8
1018
0.79 HU 4
1593
0.25 IT 70
4167
1.68 LU
715
0.56 LV 31
1282
2.42 MT 56
1035
5.41 PL 29
2766
1.05 PT 58
1697
3.42 SK 10
1384
0.72
YEAR
SPLIT HH
TOT HH %
2013 5
42911
0.01
2014
290
36519
0.79
2015
523
33627
1.56
2016
724
31673
2.29
Distribution of Split-Off Households, Total Households and incidence of Split-Off Households by year, in FR
YEAR
SPLIT HH
TOT HH %
2013
302
8733
3.46
2014
352
7913
4.45
2015
375
7011
5.35
2016
384
6161
6.23
UDB
19 selected countries, with split-off households

16. PATTERNS OF PRESENCE IN THE PANEL AND RE-ENTRIES
Patterns of Presence (P=Interviewed hh) and Absence ( -- =Non-Interviewed hh)
of Households in the panel
Re-Entries:
from the second wave, households non-interviewed one single year for «temporary» reasons will be recontacted and interviewed next year
=> intermittent presence in the interviewed sample
12 COUNTRIES WITHOUT RE-ENTRIES
14 COUNTRIES WITH RE-ENTRIES
Re-Entries:
do not contribute to the 4-years longitudinal estimates (e.g. Persistent at Risk of Poverty Rate, precision requirement in the IESS)
scarcely contribute to two-years longitudinal estimates (pooled with the other rotational panels)
contribute to the cross-sectional estimates (pooled with the other rotational panels)
UDB
26 countries

17. PATTERNS OF PRESENCE IN THE PANEL AND RE-ENTRIES
Patterns of Presence (P=Interviewed hh) and Absence ( -- =Non-Interviewed hh) of Households in the panel
Balanced Panel= 63.1% of 1st wave HH
Exits=31.1%
14 COUNTRIES WITH
RE-ENTRIES
Re-Entries=5.8%
12 COUNTRIES WITHOUT RE-ENTRIES
Balanced Panel= 74.6% of 1st wave HH
Exits=25.4% (=> including potential re-entries)
UDB
26 countries
4 years panel only

18. PATTERNS OF PRESENCE IN THE PANEL AND RE-ENTRIES
Incidence of HH in the Balanced panels, by country with Re-Entries
Incidence of HH in the Balanced panels, by country without Re-Entries
Balanced panel
Exits
Re-Entries BE
61.8
34.5
3.7 CH
65.6
26.4
8.0 EE
71.1
24.1
4.8 ES
60.9
33.4
5.7 FR
61.2
33.7
5.1 HR
58.7
37.6 HU
61.6
36.9
1.5 IT
58.8
31.3
9.9 LV
71.5
25.1
3.5 NO
23.7
15.2 PL
73.8
24.4
1.8 PT
84.4
12.7
2.9 SE
57.9
28.4
13.6 SI
51.6
45.5
3.0
Total
63.1
31.1
5.8
Balanced panel
Exits AT
62.9
37.1 BG
83.2
16.8 CY
81.4
18.6 CZ
86.9
13.1 DK
85.5
14.6 EL
63.3
36.8 FI
68.5
31.5 LU
56.8
43.2 MT
79.4
20.6 NL
60.2
39.9 RO
95.8
4.2 SK
90.6
9.4
Total
74.6
25.4
High variability in the incidence of HH successfully interviewed during 4 years.
Better performance in countries where there are no Re-Entries
UDB
26 countries

19. DISCUSSION Minimum age to be defined as a Sample Person
Since household members aged<16 at first wave are not likely to move to another private households without other samples persons (i.e. household members aged 16+ at first wave), there is not a clear advantage in lowering such a threshold.
The role of SPLIT-OFF households
A low percentage of sample persons who move to another private household are successfully interviewed. The incidence of split-off households is very heterogeneous among countries and increases with time (i.e. wave).
These households are worth of interest per sè, because they are representative of longitudinal changes in the target population.
Re-contact of non-interviewed households (Re-Entries)
About half of countries allow for re-entries in the panel (i.e. a household non-interviewed a single year is re-contacted and possibly re-interviewed next year), but also show lower balance panels incidence.
Re-Entries scarcely contribute to longitudinal estimates, and partially to cross-sectional estimates.
The potential increase in the sample attrition does not appear problematic.