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Notes on comparability of data

Comparisons between data up to 1995 and data since 1996
Better coverage of small income amounts
Detailed family types
Comparisons with previous editions

Comparisons between data up to 1995 and data since 1996

The data for the historical period (years prior to the last) are not necessarily the same as in previous editions. Data up to and including 1995 are drawn from the Survey of Consumer Finances (SCF, last conducted for reference year 1997), and data for 1996 and onwards are drawn from the Survey of Labour and Income Dynamics (SLID). For this 2001 edition of tables, all other changes from the 2000 edition are very minor.

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 on the Statistics Canada internet site (www.statcan.ca).

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.

Better coverage of small income amounts

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.

Detailed family types

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”. (See also Major income earner under Family definitions in the section on Notes and definitions.) 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.)

Comparisons with previous editions

The data for years prior to 2000 are not necessarily directly comparable to those of the 1999 edition. For example, dollar amounts are always expressed in constant dollars of the latest reference year. (See Current dollars versus constant dollars under Analytical Concepts.)

The Survey of Labour and Income Dynamics uses estimates of the target population - which are derived independently from the survey – as benchmarks for producing survey estimates. These population estimates start with a Census and are then updated using administrative data to reflect the current population of Canada. Using these population counts reduces the sampling error and coverage bias of survey estimates. It also provides consistency of estimates across household surveys. Accurate population numbers are crucial in determining estimates from a sample survey like SLID. In order to translate the results of the survey into population estimates, each individual in the sample is assigned a weight indicating the number of persons in the population represented by that sample member.

Periodically, the weights used in the survey are updated to reflect the availability of new population benchmarks provided by a new census and new annual inter-censal estimates. When this happens, the weights are revised historically in order to maintain a consistent time series. Methodological improvements in the derivation of weights may also be implemented in a weight revision.

The most recent historical weight revision for the Survey of Labour and Income Dynamics occurred with the release of data for 2000. It was carried out on data back to 1980, such that figures for the entire time series changed. Traditionally, weights are derived using population benchmarks by province, age and sex. Since the 2000 weight revision, the weights in SLID also respect population benchmarks by household size and economic family size.



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Date Modified: 2008-10-17 Important Notices