4. Method of survey For the overall analysis of PPC within the purview of this survey, a variety of methods were employed, e.g. in-depth interviews, questionnaires, personal visits and research on a wide variety of documents. As the objectives of the survey include investigation of reality, analysis of cases and presentation of recommendations, attempts were made to employ rational methods to achieve these objectives. Accordingly, the present survey was carried out on the basis of reviewing the earlier testimonies by North Korean defectors and papers on the PPC and detailed questions were designed in consideration of the issue of forced repatriation and papers published. Questionnaires and indepth interviews were carried out on the basis of questionnaires especially designed for the purpose of the survey as follows: 1) Analysis of documents Related data were collected domestically and abroad20 for the survey and included, among others, overall analysis of earlier records of those North Koreans experienced in PPC (both victims and perpetrators), victims of forced repatriation, testimonies, surveys and research reports. The most recent data were collected to review any evidence of progress by North Korea to observe international human rights instruments it has acceded to. Similar cases in other countries, such as within the former Soviet Socialist bloc, were reviewed for the purpose of comparison. 20 Yoon Yeo-sang, “Analysis of Documents on North Korean Human Rights,” NKDB, Seoul, 2008. 30