The KLIPS sample is an equal probability sample of households from 7 metropolitan cities and urban areas in 8 provinces (excluding Cheju Island) and was designed to interview 5000 households and their members (aged 15 and over).
The final number of individuals successfully interviewed during the 1st Wave (1998) was 13,319.
The KLIPS sample is an equal probability sample of households from 7 metropolitan cities and urban areas in 8 provinces (excluding Cheju Island) and was designed to interview 5000 households and their members (aged 15 and over, excluding people in military service or facility residents). The final number of individuals that we successfully interviewed during the 1st Wave (1998) was 13,319.
These 5000 households and their members make up the original panel households and household members. To sample primary sampling units and then the households therein, KLIPS used the sampling frame for the 1995 Korea (mid-term) Census. Out of the Census unit area (total = 21,675), a total of 951 sampling unit areas were finally selected, and from each sampling unit, 5-6 households were randomly selected. The households and members thus selected are designed to represent the adult population (aged 15 and over) residing in urban areas.
Follow-up Rules: Starting from the 2nd Wave (1999), Individuals that form family ties to the original panel members are added to the original sample. For example, if a panel member gets married and forms an independent household with his/her spouse, then, his/her spouse becomes a ‘new respondent’ to the original panel and the couple is followed and interviewed thereafter. On the other hand, if one of the panel members moves into a non-member household, through getting married for instance, he/she is also followed and his/her spouse’s household members are interviewed. In this way, the size of the sample members grows and expands over the waves. This method of incorporating related households and individuals into the sample allows the expanded sample to reflect on-going demographic dynamics of the original panel members. When a panel member moves out of the original household, through divorce for instance, he/she is also tracked as long as he/she lives with his/her children.
Census PSU and PSU sampled into KLIPS
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City, Province, Census, PSU, KLIPS PSU
City, Province |
Census |
PSU |
Households |
Seoul |
5,186 |
227 |
227 |
Busan |
1,841 |
176 |
97 |
Daegu |
1,212 |
155 |
64 |
Inchon |
1,116 |
150 |
59 |
Gwangju |
607 |
106 |
32 |
Daejun |
592 |
101 |
31 |
Ulsan |
456 |
70 |
24 |
Gyunggi-do |
3,624 |
280 |
167 |
Kangwon-do |
725 |
165 |
26 |
Choongcheongbuk-do |
694 |
159 |
22 |
Choongcheongnam-do |
865 |
122 |
25 |
Jeollabuk-do |
967 |
170 |
40 |
Jeollanam-do |
996 |
152 |
25 |
Gyeongsangbuk-do |
1,372 |
129 |
54 |
Gyeongsangnam-do |
1,422 |
220 |
58 |
Total |
21,675 |
2,382 |
951 |
Additional Sampling(2009, 2018)
Initial contact with the 5000 households originally sampled out of the Census PSU met with a success rate of about 75% (3,773 households), and the rest (25%, 1,227 households) were replaced by other randomly selected households in the same PSU.[1] The total number of individuals in the 5,000 interviewed households amounted to 17,505. As we do not interview household members 14 years old or younger, the total number of individuals personally interviewed in the base year (1998) was 13,319 (out of 13,738 persons).
Field work for KLIPS usually starts in April and continues up to October each year. However, in the base year, field work was delayed by a month (June to October). The majority (about 2/3) of interviews were finished by the end of August.
As mentioned above, KLIPS is based on an expanding sample. That is, we add new respondents to the original household sample, while following any original panel members who move out of the original household due to divorce, separation, etc. New respondents include non-family members who marry the family member and move into the original household, as well as the doubling up of non-panel family members who were once economically independent, etc. We call new independent households created by original panel members ‘branch households’ (Bunga Gagu). So far up to the 23rd Wave, a total of 2,630 new branch households were created.
Additional Sampling(2009, 2018)
To overcome the limitations posed by panel household attrition and urban concentration and improve the representativeness of the panel data, additional sampling was carried out in 2009. KLIPS used ‘two-stage cluster systematic sampling’, which is to sample firstly using unit area of the 2005 Korea Census as the sampling frame, then selecting random households within the area. In the first stage, unit areas were selected using a different method according to the administrative district. ‘Unit Area Characteristics Value(value calculated with the number of households and single-family households)’ is used to choose ‘–dong’ unit area and ‘Probability Proportionate Sampling(sampling proportionately to the household number of the unit area)’ is used for ‘-eup’ and ‘-myeon’ district. In the second stage, five households were randomly selected for each sample unit area chosen in the first stage. Total of 1,415 households was additionally sampled using this procedure.
As the sample was increasingly unable to reflect the population due to reasons such as attrition in the course of over 20 years, a study on additional sample was conducted and sampling was performed in 2017 and 2018. The sampling frame for the survey population was based on the 2016 Korea Census. For the first step, enumeration districts are aligned in the order of region, followed by the number of households for each strata, and enumeration district are sampled using PPS where probability is proportional to the number of household in each enumeration districts. In the second step, the list of households will be created from each enumeration district and 10 households will be sampled using Systemic Sampling. In the event of failure to secure the panel, the household in question will be replaced with the immediately adjacent household. Total of 5,044 households was additionally sampled using this procedure.
Additional Sampling(2009, 2018)
KLIPS today has three panels in one dataset; 98 sample and 09, 18 Consolidated sample. The 98 sample contains data from the 5,000 original households starting from Wave 1 (1998).
The 09 consolidated sample contains additional households sampled in 2009. For the 09 consolidated data, all the households that responded in 2009 (Wave 12) make up the original sample. Thus the 09 consolidated sample consists of not only the 1,415 households additionally included in 2009, but also the existing households (98 sample + branch households) who responded to Wave 12 survey, for a total of 5,306.
The 18 consolidated sample combines the pool of 7,090 households successfully surveyed in 2018 with the 5,044 that were newly added. the 18 consolidated sample has four components: the original sample household from 09 consolidated sample (5,598 households), the branch households stemming from 09 consolidated sample (1,111 households), 98 sample not included in 09 consolidated sample (381 households), and 5,044 households added in 2018.