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Starting with reference year 1996, the Survey of Labour and Income Dynamics (SLID) replaced the annual Survey of Consumer Finances (SCF) as the official source of family income in Canada. This means that data up to and including 1995 are drawn from SCF (last conducted for reference year 1997), and data for 1996 and onwards are drawn from the SLID (which was introduced in 1993).
Different surveys will produce slightly different estimates on the same topics due to a variety of factors. Every attempt was made to minimize and monitor these differences between the two income surveys, while nonetheless making some important improvements in survey practices. Before replacing the SCF series with SLID, a careful study was done on the overlapping reference years, particularly the years 1996 and 1997, as SLID only acquired its full sample size in 1996. The results of the study are contained in the Income Statistics Division research paper, A Comparison of the Results of the Survey of Labour and Income Dynamics (SLID) and the Survey of Consumer Finances (SCF) 1993-1997: Update (75F002MIE99007). All ISD research papers are available free of charge.
In short, it was found that the two surveys told essentially the same story for all of the main income concepts. It is still possible, nonetheless, that for some characteristics the data trends could reveal a “break” as a result of the change in survey. Such a break would likely appear as a noticeable upward or downward shift in a data series between the years 1995 and 1996. It represents a change in the data which is attributable to the two surveys having different samples and different methods (such as the use of tax data in the case of SLID), rather than a true change in the characteristics of the population. Users are advised to take note of the following survey differences which are known to exist and to have had an impact on the data trends at some detailed levels.
One notable improvement that occurred as a result of new survey techniques introduced in SLID is better coverage of small income amounts received by respondents. It has been observed in surveys conducted by questionnaire that respondents tend to forget or neglect small income amounts they received in the past. This means an underestimation of income in general, and in particular, it means that many people who received a small amount of income instead report no income at all (there are differences, however, depending on whether the income concept includes or excludes government transfers).
The use of administrative income tax files in SLID for the majority of sample respondents means that there is considerably better coverage of non-zero amounts of income, and in general, a greater number of recipients of most kinds of income. Another technique used by SLID which may have improved coverage is that, even for respondents who report income by interview instead of via their tax records, there are two chances to prompt them for income sources, and therefore a greater likelihood of capturing an amount. This is because some income concepts are touched on in the January interview and then covered in the May interview, where it is possible to remind the respondent of a positive response in January. The types of income for which such “dependent interviewing” is used are earnings (from employment or self-employment), employment insurance benefits, social assistance, and workers' compensation.
The standard published “detailed family types” for economic families have changed in one regard. In the SCF, they are derived with reference to the “head of family”. In SLID, the same categories are used but in reference to the “major income earner”. SLID dropped the concept of head of family entirely, as it has little relevance in a modern context. But some sort of prioritization of people within a family is useful to uniquely identify the type of family, even if it is somewhat arbitrary.
The change in family concepts resulting from the transition from SCF to SLID has not affected data produced for the entire population of families consisting of two or more persons. However, for some of the detailed family types, the estimated number of families underwent a one-time increase or decrease between 1995 and 1996. Without drawing conclusions about the precise net effects of these changes, the following points can be made.
First, whereas the previous definition always gave husbands the status of head of family rather than wives, with the major income earner concept there is no distinction by sex, and it is possible for the wife to qualify. Since it still holds that wives are on average younger than husbands at least for older couples, this has caused a shift from elderly families to non-elderly families.
Second, the head of family concept gave preference to parents over their adult children and, where there is no husband-wife or parent-child relationship in the family, it gave preference to older members over younger ones. Now, younger adults are much more likely to qualify as major income earners than they did as heads of families. As a result, we see significant decreases in the number of “other elderly families” and “married couples with other relatives”, and a large increase in the number of “other non-elderly families”. (See the section “Family definitions” for the precise definitions of family types.)
Data from different editions are not directly comparable. Every edition has some modifications done on data. The modification which is applied every year is the expression of all dollars amounts in constant dollars of the latest reference year. (See “Current dollars versus constant dollars”.)
Periodically, the weights are updated to reflect the availability of new population benchmarks provided by a new census. The most recent multi-year weight revision for the Survey of Labour and Income Dynamics and the Survey of Consumer Finance occurred with the release of data for 2003, when the population projections based on the 2001 Census of Population were incorporated.
The improvements to survey weights during the 2000 and 2003 historical revisions were part of a comprehensive project at Statistics Canada regarding the weighting strategies in the main annual surveys on income, expenditures, and wealth. Weights are typically adjusted using population benchmarks by province, age and sex. Since the 2000 weight revision, the weights in SLID and SCF also respect population benchmarks by household size and economic family size.
Since the 2003 revision, the weights from 1990 to the current period include adjustments based on the annual T4 file from Canada Revenue Agency (CRA), which is a compilation of employer remittances for the purposes of payroll taxes. For more, please refer to the free research paper, Survey of Labour and Income Dynamics: 2003 historical revision, Statistics Canada,
The 2003 historical revision was followed up with a minor weight revision for 2003 only, timed with the release of data for 2004