Sample design

Cohort A

Stratification

A. The prefectures of Japan were classified into eight blocks.

B. The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.

1. 13 major cities (Sapporo, Sendai, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Nagoya, Kyoto, Osaka, Kobe, Hiroshima, Kitakyushu, Fukuoka)

2. Other cities

3. Towns or villages

(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.

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

A. The survey area established at the time of the 1990 census was used as the survey point to serve as the primary extraction unit.

B. 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.

C． 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.

Number of survey areas in strata (total)

———-　　= Extraction interval

Number of survey sites extracted in stratum

D. 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.

E. 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.).

F. 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.

H. 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

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

A. The prefectures of Japan were classified into eight blocks.

B. The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.

1. 14 major cities (Sapporo, Sendai, Saitama, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Nagoya, Kyoto, Osaka, Kobe, Hiroshima, Kitakyushu, Fukuoka)

2. Other cities

3. Towns or villages

(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.

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

A. The prefectures of Japan were classified into eight blocks.

B. The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.

1. 18 major cities (Sapporo, Sendai, Saitama, Chiba, Tokyo metropolitan area, Yokohama, Kawasaki, Niigata, Shizuoka, Hamamatsu, Nagoya, Kyoto, Osaka, Sakai, Kobe, Hiroshima, Kitakyushu, Fukuoka)

2. Other cities

3. Towns or villages

(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.

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.

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

A. The prefectures of Japan were classified into eight blocks.

B. The number of cities in each block. Within each block, the cities were further classified and stratified by city size as follows.

1. 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)

2. Other cities

3. Towns or villages

(Note) Cities in this section are defined as areas where municipal government was in effect as of April 1, 1993.

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