Codes and Frequencies
YEAR indicates the year the survey was completed.
Although in most surveys data were collected in the same year, others include diaries kept in different years. In 1965 and 1998 when diaries were combined from two different surveys (SURVEY) and collected in different years, YEAR and SAMPLE are not the same.
Detailed information about each sample is available elsewhere.
- All persons.
- 1930, 1965, 1975, 1985, 1993, 1995, 1998, 2003-2012, 2018