### I. Overview of the survey

### 1. The seventh national survey on migration

The Seventh National Survey on Migration aims to clarify recent migration trends and to obtain fundamental data for projecting future migration trends, followed by six surveys in the past (1976, 1986, 1991, 1996, 2001, 2006). The Seventh Survey was implemented on July 1st, 2011 with the cooperation of the Statistics and Information Department, Ministry of Health, Labour and Welfare, prefectural governments, the cities and special wards that operate public health centers and the public health centers. However, due to the Great East Japan Earthquake, the survey was cancelled in the prefectures of Iwate, Miyagi, and Fukushima. For Hokkaido, the survey was postponed and eventually held on September 1st of the same year. The items surveyed are nearly identical to those of the previous survey. These include residential history for the household heads and members of the household, prefectures in which they have lived, experience of leaving home, and prospects of residence 5 years ahead.

### 2. Methodology and response rate

The subjects of the survey were household heads and household members of all households in 288 survey districts (of 300 randomly selected districts from total survey districts of the 2011 Comprehensive Survey on Living Conditions, 12 districts were excluded due to the Great East Japan Earthquake). Household heads were asked to complete the questionnaires, which were distributed and collected by enumerators.

There were 15,449 eligible households for the survey. Out of these, questionnaires were distributed to 12,884 households and 11,546 households returned the questionnaire. Collected questionnaires that were left completely blank or from which critical information was missing were judged as invalid, leaving a final total of 11,353 valid questionnaires for analysis. This gave a response rate of 74.7% and a valid response rate of 73.5% out of eligible households. The response rate was 89.6% and the valid response rate was 88.1% out of households to which questionnaires were distributed.

The distribution of respondents of this survey was compared to that of the Current Population Estimates as of October 1st, 2011 by regional block (excluding the prefectures of Iwate, Miyagi, and Fukushima) reported by the Statistics Bureau, Ministry of Internal Affairs and Communications. It was found that the percentage of respondents for the Seventh National Survey on Migration was lower in large metropolitan areas such as Tokyo and Osaka areas, but higher in the Chubu, Hokuriku, and Chukyo areas.

A comparison of the distribution of survey respondents to that of the Current Population Estimates as of October 1 $ ^{st} $ , 2011 by 5-year age groups indicated that the percentages of survey respondents in their 20s and 30s were lower in the survey, especially from the late 20s to early 30s. For example, the percentage of people in their late 20s accounts for 5.7% of the total estimated population, but the corresponding percentage is only 5.1% for the survey.

This comparison implies the difficulties in distributing and collecting questionnaires to/from households in urban areas and those consisting of relatively young people. The percentage of respondents aged 75 and older was also lower in the survey. In addition to the difficulties in distributing and collecting questionnaires, this may also have been affected by the fact that residents of long-term care facilities were not included in the survey. Consequently, one should be careful in interpreting the data from the survey.