7.13. Population censuses can be used to benchmark some of the data collected through other means or estimated. They can also be used as a sampling frame for surveys. Such approaches could be relevant for obtaining data on persons moving temporarily abroad under a mode 4 regime and to obtain a sense of medium- to long-term developments, including the importance of outbound mode 4 for the country. More specific surveys or modules can then gather additional details focusing on employment at home and abroad, adding questions relevant to mode 4. For example, to identify more specifically persons who went abroad temporarily in the context of mode 4, one could add the following questions:
(a) Have you travelled abroad for work in the past [x]  months? Yes/No;
(b) If Yes, for what purposes?
(i) To fulfil a contract;
(ii) To negotiate a contract or establish an affiliate.
To avoid confusion with work-related movements not covered by mode 4, questions and response alternatives are needed to identify the country of residence of the employer at the time.
7.14. If such questions are identified as potential sources of information, compilers are encouraged to approach the staff in charge of the census. The contents of the questions respond to various needs, and it is necessary to analyze if and how a population census could be used, either by drawing on existing information or by adding a module or questions. Given the long preparation time necessary to develop and conduct a census, compilers should contact the staff in charge of the census during the early stages of its design.
Include page: Country experience: Canada (Chapter 7)
Next: D. Household surveys
 It should, however, be kept in mind that an increasing number of countries are moving from traditional questionnaires to a register-based census, which may reduce the potential use of that source in the context of the present Guide.
 Number of months to be determined by the frequency of and period covered by the census.
 See chapter 1 and box V.2 of MSITS 2010 for more information on the identification of the employer-employee relationship.