Sample design
This survey was conducted from 1993 (Wave 1) to 2021 (Wave 29).
Cohort A
Stratification
The prefectures of Japan were classified into eight blocks.
The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.
13 major cities (Sapporo, Sendai, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Nagoya, Kyoto, Osaka, Kobe, Hiroshima, Kitakyushu, Fukuoka)
(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.
Towns or villages
Sample distribution
Depending on the size of the estimated population in each city-size stratum, a sample size of 1,500 was proportionally distributed, taking into account the age structure and marital status (the number of people aged 24-34 by age and marital status as of March 31, 1992).
Sampling
The survey area established at the time of the 1990 census was used as the survey point to serve as the primary extraction unit.
The number of survey points (census tracts) The number of survey sites (census tracts) was determined by calculating the number of samples assigned to each stratum so that the sample size per survey site would be 12.
Extraction of study sites (study area) was carried out using the equal interval method by calculating the extraction intervals as follows for the strata where the number of extraction sites within a stratum was assigned to two or more sites.
The order of cities, towns, and villages in each stratum in the extraction follows the order of the “Prefectural and Municipal Code Table” at the time of the 1990 census.
The respondents at the survey points were extracted from the Basic Resident Register using the equal interval extraction method according to the address of the survey point (specifying the town, street, city block, street number, etc.).
Since this survey was designed to be a survey with a specified number of completions, a reserve respondent 3 was added to the regular respondent 1 above.
The number of samples by stratum and the number of survey sites obtained as a result of the above work are shown in Table-1.
Table 1 Estimated population size, sample size, and number of survey sites by stratum for Cohort A
Table 1-1 Estimated population size
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
272,755 |
328,511 |
177,644 |
778,910 |
Tohoku |
143,956 |
710,759 |
439,852 |
1,294,567 |
Kanto |
2,261,067 |
3,035,727 |
612,586 |
5,909,380 |
Chubu |
330,121 |
1,982,543 |
787,642 |
3,100,306 |
Kinki |
791,651 |
1,684,208 |
331,368 |
2,807,227 |
Chugoku |
158,655 |
578,830 |
220,257 |
957,742 |
Shikoku |
0 |
343,032 |
175,300 |
518,332 |
Kyushu |
327,575 |
1,019,476 |
580,010 |
1,927,061 |
Total |
4,285,780 |
9,683,086 |
3,324,659 |
17,293,525 |
Table 1-2 Sample size
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
24 |
36 |
12 |
72 |
Tohoku |
12 |
60 |
36 |
108 |
Kanto |
192 |
264 |
60 |
516 |
Chubu |
36 |
168 |
72 |
276 |
Kinki |
72 |
144 |
24 |
240 |
Chugoku |
12 |
48 |
24 |
84 |
Shikoku |
0 |
36 |
12 |
48 |
Kyushu |
24 |
84 |
48 |
156 |
Total |
372 |
840 |
288 |
1,500 |
Table 1-3 Number of survey sites
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
2 |
3 |
1 |
6 |
Tohoku |
1 |
5 |
3 |
9 |
Kanto |
16 |
22 |
5 |
43 |
Chubu |
3 |
14 |
6 |
23 |
Kinki |
6 |
12 |
2 |
20 |
Chugoku |
1 |
4 |
2 |
7 |
Shikoku |
0 |
3 |
1 |
4 |
Kyushu |
2 |
7 |
4 |
13 |
Total |
31 |
70 |
24 |
125 |
Cohort B
Stratification
The sample design for Cohort B was the same as that for Cohort A except for the sample size distribution. The distribution of Cohort A respondents closely matched that of the national census, with the only exception being that the proportion of unmarried single individuals was slightly lower than that in the national census. Accordingly, the proportion of unmarried single individuals in Cohort B was taken into account when allocating the number of samples.
Sample distribution
Depending on the size of the estimated population in each city-size stratum, a sample size of 500 was allocated proportionally, taking into account the age structure and marital status (number of people aged 24-27 as of March 31, 1996, by age and marital status, and number of single-person households with no marital status). The sample size by stratum and the number of survey sites are shown in Table-2.
Sampling
For each official respondent, reserve respondents were selected as follows depending on marital status and household circumstances: 3 reserve respondents for each married respondent, 3 reserve respondents for each unmarried respondent not in a single household, and 5 reserve respondents for each unmarried respondent in a single household.
Table 2 Estimated population size, sample size, and number of survey sites by stratum for Cohort B
Table 2-1 Estimated population size
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
315,837 |
354,942 |
163,782 |
834,561 |
Tohoku |
165,648 |
717,759 |
403,002 |
1,286,409 |
Kanto |
2,759,343 |
3,683,433 |
623,364 |
7,066,140 |
Chubu |
385,263 |
2,239,332 |
831,210 |
3,455,805 |
Kinki |
942,807 |
1,994,082 |
345,852 |
3,282,741 |
Chugoku |
180,561 |
607,938 |
209,568 |
998,067 |
Shikoku |
0 |
359,337 |
168,459 |
527,796 |
Kyushu |
363,696 |
1,041,798 |
557,448 |
1,962,942 |
Total |
5,113,155 |
10,998,621 |
3,302,685 |
19,414,461 |
Table 2-2 Sample size
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
8 |
10 |
4 |
22 |
Tohoku |
4 |
20 |
9 |
33 |
Kanto |
72 |
98 |
14 |
184 |
Chubu |
9 |
61 |
20 |
90 |
Kinki |
25 |
55 |
5 |
85 |
Chugoku |
4 |
15 |
4 |
23 |
Shikoku |
0 |
10 |
4 |
14 |
Kyushu |
10 |
26 |
13 |
49 |
Total |
132 |
295 |
73 |
500 |
Table 2-3 number of survey sites
13 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
2 |
3 |
1 |
6 |
Tohoku |
1 |
5 |
3 |
9 |
Kanto |
16 |
22 |
5 |
43 |
Chubu |
3 |
14 |
6 |
23 |
Kinki |
6 |
12 |
2 |
20 |
Chugoku |
1 |
4 |
2 |
7 |
Shikoku |
0 |
3 |
1 |
4 |
Kyushu |
2 |
7 |
4 |
13 |
Total |
31 |
70 |
24 |
125 |
Cohort C
Stratification
The prefectures of Japan were classified into eight blocks.
The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.
14 major cities (Sapporo, Sendai, Saitama, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Nagoya, Kyoto, Osaka, Kobe, Hiroshima, Kitakyushu, Fukuoka)
(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.
Towns or villages
Sample distribution
Depending on the size of the estimated population in each city size stratum, 836 samples were proportionally distributed, taking into account the age structure and marital status (number of people aged 24-29 years as of March 31, 2003, by age and marital status). The sample size and number of survey sites by stratum are shown in Table-3.
Sampling
Between 4 and 9 respondents were selected for each survey site depending on the age and marital status distributions for each city size stratum. Reserve respondents were identified as follows depending on marital status and household circumstances: 3 reserve respondents for each married respondent, 4 reserve respondents for each unmarried respondent not in a single household, and 7 reserve respondents for each unmarried respondent in a single household
Table 3 Estimated population size, sample size, and number of survey sites by stratum for Cohort C
Table 3-1 Estimated population size
14 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
540,756 |
613,383 |
265,566 |
1,419,705 |
Tohoku |
317,436 |
1,244,232 |
665,448 |
2,227,116 |
Kanto |
4,679,379 |
6,137,133 |
1,135,146 |
11,951,658 |
Chubu |
614,394 |
4,021,920 |
1,447,863 |
6,084,177 |
Kinki |
1,565,124 |
3,533,046 |
628,206 |
5,726,376 |
Chugoku |
337,476 |
1,169,547 |
385,989 |
1,893,012 |
Shikoku |
0 |
681,645 |
299,001 |
980,646 |
Kyushu |
675,927 |
1,902,615 |
962,382 |
3,540,924 |
Total |
8,730,492 |
19,303,521 |
5,789,601 |
33,823,614 |
Table 3-2 Sample size
14 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
11 |
15 |
6 |
32 |
Tohoku |
6 |
29 |
17 |
52 |
Kanto |
118 |
158 |
29 |
305 |
Chubu |
19 |
97 |
35 |
151 |
Kinki |
40 |
87 |
14 |
141 |
Chugoku |
8 |
28 |
9 |
45 |
Shikoku |
0 |
18 |
6 |
24 |
Kyushu |
18 |
45 |
23 |
86 |
Total |
220 |
477 |
139 |
836 |
Table 3-3 Number of survey sites
14 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
2 |
3 |
1 |
6 |
Tohoku |
1 |
5 |
3 |
9 |
Kanto |
17 |
21 |
5 |
43 |
Chubu |
3 |
14 |
6 |
23 |
Kinki |
6 |
12 |
2 |
20 |
Chugoku |
1 |
4 |
2 |
7 |
Shikoku |
0 |
3 |
1 |
4 |
Kyushu |
2 |
7 |
4 |
13 |
Total |
32 |
69 |
24 |
125 |
Cohort D
Stratification
The prefectures of Japan were classified into eight blocks.
The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.
18 major cities (Sapporo, Sendai, Saitama, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Niigata, Shizuoka, Hamamatsu, Nagoya, Kyoto, Osaka, Sakai, Kobe, Hiroshima, Kitakyushu, Fukuoka)
(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.
Towns or villages
Sample distribution
Depending on the size of the estimated population in each city size stratum, 836 samples were proportionally distributed, taking into account the age structure and marital status (number of people aged 24-28 years as of March 31, 2008, by age and marital status). The sample size and number of survey sites by stratum are shown in Table-4.
Sampling
Between 4 and 9 respondents were selected for each survey site depending on the age and marital status distributions for each city size stratum. Reserve respondents were identified as follows depending on marital status and household circumstances: 3 reserve respondents for each married respondent, 4 reserve respondents for each unmarried respondent not in a single household, and 7 reserve respondents for each unmarried respondent in a single household
Table 4 Estimated population size, sample size, and number of survey sites by stratum for Cohort D
Table 4-1 Estimated population size
18 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
66,227 |
69,550 |
24,681 |
160,458 |
Tohoku |
37,916 |
175,721 |
46,499 |
260,136 |
Kanto |
539,215 |
709,813 |
64,797 |
1,313,825 |
Chubu |
133,722 |
451,572 |
69,476 |
654,770 |
Kinki |
206,915 |
385,174 |
34,559 |
626,648 |
Chugoku |
37,244 |
155,344 |
15,805 |
208,393 |
Shikoku |
0 |
92,753 |
15,981 |
108,734 |
Kyushu |
85,115 |
290,154 |
65,475 |
440,744 |
Total |
1,106,354 |
2,330,081 |
337,273 |
3,773,708 |
Table 4-2 Sample size
18 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
11 |
11 |
4 |
26 |
Tohoku |
7 |
29 |
8 |
44 |
Kanto |
89 |
118 |
10 |
217 |
Chubu |
23 |
75 |
12 |
110 |
Kinki |
34 |
63 |
5 |
102 |
Chugoku |
6 |
26 |
3 |
35 |
Shikoku |
0 |
15 |
3 |
18 |
Kyushu |
14 |
48 |
11 |
73 |
Total |
184 |
385 |
56 |
625 |
Table 4-3 Number of survey sites
18 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
2 |
3 |
1 |
6 |
Tohoku |
1 |
7 |
2 |
10 |
Kanto |
18 |
22 |
3 |
43 |
Chubu |
5 |
17 |
3 |
25 |
Kinki |
7 |
11 |
2 |
20 |
Chugoku |
1 |
6 |
1 |
8 |
Shikoku |
0 |
4 |
1 |
5 |
Kyushu |
2 |
9 |
2 |
13 |
Total |
36 |
79 |
15 |
130 |
Cohort E
Stratification
The prefectures of Japan were classified into eight blocks.
The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.
21 major cities (Sapporo, Sendai, Saitama, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Sagamihara, Niigata, Shizuoka, Hamamatsu, Nagoya, Kyoto, Osaka, Sakai, Kobe, Okayama, Hiroshima, Kitakyushu, Fukuoka, Kumamoto)
(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.
Towns or villages
Sample distribution
Depending on the size of the estimated population in each city-size stratum, a sample size of 625 was proportionally distributed, taking into account the age structure and marital status (the number of people aged 24-34 by age and marital status as of March 31, 1992).
Sampling
Between 4 and 9 respondents were selected for each survey site depending on the age and marital status distributions for each city size stratum. Reserve respondents were identified as follows depending on marital status and household circumstances: 3 reserve respondents for each married respondent, 4 reserve respondents for each unmarried respondent not in a single household, and 7 reserve respondents for each unmarried respondent in a single household
Table 5 Estimated population size, sample size, and number of survey sites by stratum for Cohort E
Table 5-1 Estimated population size
21 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
60,858 |
58,665 |
20,731 |
140,254 |
Tohoku |
34,186 |
151,987 |
40,590 |
226,763 |
Kanto |
529,768 |
631,066 |
47,369 |
1,208,203 |
Chubu |
125,493 |
419,440 |
50,945 |
595,878 |
Kinki |
194,725 |
345,567 |
29,450 |
569,742 |
Chugoku |
54,925 |
122,797 |
12,914 |
190,636 |
Shikoku |
0 |
83,412 |
13,903 |
97,315 |
Kyushu |
101,576 |
248,224 |
53,685 |
403,485 |
Total |
1,101,531 |
2,061,158 |
269,587 |
3,432,276 |
Table 5-2 Sample size
21 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
11 |
11 |
4 |
26 |
Tohoku |
6 |
28 |
8 |
42 |
Kanto |
96 |
115 |
8 |
219 |
Chubu |
23 |
76 |
10 |
109 |
Kinki |
35 |
63 |
5 |
103 |
Chugoku |
10 |
23 |
2 |
35 |
Shikoku |
0 |
15 |
3 |
18 |
Kyushu |
18 |
45 |
10 |
73 |
Total |
199 |
376 |
50 |
625 |
Table 5-3 number of survey sites
21 major cities |
Other cities |
Towns or villages |
Total |
|
---|---|---|---|---|
Hokkaido |
2 |
2 |
1 |
5 |
Tohoku |
1 |
6 |
2 |
9 |
Kanto |
19 |
23 |
2 |
44 |
Chubu |
5 |
15 |
2 |
22 |
Kinki |
7 |
13 |
1 |
21 |
Chugoku |
2 |
5 |
1 |
8 |
Shikoku |
0 |
3 |
1 |
4 |
Kyushu |
4 |
9 |
2 |
15 |
Total |
40 |
76 |
12 |
128 |