At the heart of the survey's objectives is the understanding of the economic well-being of Canadians: what economic shifts do individuals and families live through, and how does it vary with changes in their paid work, family make-up, receipt of government transfers or other factors? The survey's longitudinal dimension makes it possible to see such concurrent and often related events.
Data release – May 12, 2005
The Survey of Labour and Income Dynamics (SLID) complements traditional survey data on labour market activity and income with an additional dimension: the changes experienced by individuals over time. At the heart of the survey's objectives is the understanding of the economic well-being of Canadians: what economic shifts do individuals and families live through, and how does it vary with changes in their paid work, family make-up, receipt of government transfers or other factors? The survey's longitudinal dimension makes it possible to see such concurrent and often related events.
SLID was the first Canadian household survey to provide national data on the fluctuations in income that a typical family or individual experiences over time which gives greater insight on the nature and extent of low income in Canada. Added to the longitudinal aspect are the "traditional" cross-sectional data: the primary Canadian source for income data and providing additional content to data collected by the Labour Force Survey (LFS).
Particularly in SLID, the focus extends from static measures (cross-sectional) to the whole range of transitions, durations, and repeat occurrences (longitudinal) of people's financial and work situations. Since their family situation, education, and demographic background may play a role, the survey has extensive information on these topics as well.
The survey data are used by federal (Human Resources and Skills Development Canada, Finance, Canada Mortgage and Housing Corporation , etc.) and provincial departments to formulate social policies and programs. Non-government organizations, private consultant firms and academics also use SLID data to do research to support their positions and to lobby governments for social changes. Individuals and families can use the data to compare their earnings and income situations with those of similar types of family compositions.
All individuals in Canada, excluding residents of the Yukon, the Northwest Territories and Nunavut, residents of institutions and persons living on Indian reserves. Overall, these exclusions amount to less than 3 percent of the population.
The questionnaire was designed for Computer-Assisted Telephone Interview, which means that as the questions were developed, the associated logical flows into and out of the questions were programmed. This included specifying the type of answer required, the minimum and maximum values, on-line edits associated with the questions and what to do in case of item non-response. The initial version of the questionnaire was focus-group tested. When applicable, questions used in other Statistics Canada surveys were implemented in SLID to improve comparability across surveys.
This is a sample survey with a cross-sectional design and a longitudinal follow-up.
The samples for SLID are selected from the monthly Labour Force Survey (LFS, record number 3701) and thus share the latter's sample design. The LFS sample is drawn from an area frame and is based on a stratified, multi-stage design that uses probability sampling. The total sample is composed of six independent samples, called rotation groups, because each month one sixth of the sample (or one rotation group) is replaced.
The SLID sample is composed of two panels. Each panel consists of two LFS rotation groups and includes roughly 17,000 households. A panel is surveyed for a period of six consecutive years. A new panel is introduced every three years, so two panels always overlap.
Responding to this survey is voluntary.
Data are collected directly from survey respondents and extracted from administrative files.
For each sampled household in SLID, up to 12 interviews are conducted over a six-year period. Every year in January, interviewers collect information regarding respondents' labour market experiences during the previous calendar year. Information on educational activity and family relationships is also collected at that time. The demographic characteristics of family and household members represent a snapshot of the population as of the end of each calendar year.
Every May information on income is collected from the same sampled households. The income interview is deferred until May to take advantage of income tax time when respondents are more familiar with their income situation. The reference period for income is the previous calendar year.
To reduce response burden, respondents can give Statistics Canada permission to use their T1 tax information for the purposes of SLID. Those who do so are only contacted for the labour interviews. Over 80% of SLID's respondents give their consent to use their administrative records.
SLID interviews are conducted over the telephone using computer-assisted interviewing (CAI). The interviewer reads the questions as they appear on the computer screen and keys in the reported information. Skip-patterns and edits are built into the collection software, allowing interviewers to immediately detect and resolve response inconsistencies. Collection of date-related information (e.g., employment spells, jobless spells, interruption of work), is greatly improved by the use of such an interactive data capture technique. Another advantage of the CAI technology is the feeding back of details from the previous interview, helping respondents to recall past events.
Proxy response is accepted in SLID. This procedure allows one household member to answer questions on behalf of any or all other members of the household, provided he or she is willing to do so and is knowledgeable.
A series of verifications took place to ensure that the records were consistent and that collection and capture of the data did not introduce errors. Reported data were examined for completeness and consistency using automated edits coupled with manual review. Some responses reporting uncommon values or characteristics were processed manually.
The primary method employed for imputing income data in this survey is to use the previous year's data, updated for any changes in circumstances. Only in the absence of such data are income figures imputed using the "nearest neighbour" technique in SLID.
Amounts received through certain government programs, such as child tax benefits, the Goods and Services Harmonized Sales Tax Credit, and the Guaranteed Income Supplement, are also derived from other information. Data obtained from the tax route are complete and do not need imputation.
The estimation of population characteristics from a survey is based on the premise that each sampled unit represents, in addition to itself, a certain number of unsampled units in the population. A basic survey weight is attached to each record to indicate the number of units in the population that are represented by that unit in the sample.
For each reference year, SLID produces two sets of weights: one is representative of the initial population (the longitudinal weights) while the other is representative of the current population (the cross-sectional weights). For the production of the cross-sectional weights, SLID combines two independent samples and assigns a probability of selection to individuals who joined the sample after the panel was selected.
Two types of adjustment are applied to the basic survey weights in order to improve the reliability of the estimates. The basic weights are first inflated to compensate for non-response. The non-response adjusted weights are then further adjusted to ensure that estimates on relevant population characteristics would respect population totals from sources other than the survey.
The first set of population totals used for SLID is based on Statistics Canada's Demography Division population counts for different age/sex groups as well as counts by household and family size at the provincial level. These annual population totals are based in large part on totals from the Census of population.
The second set of totals is derived from Canada Revenue Agency (CRA) administrative data (T4 file) and is intended to ensure that the weighted distribution of income (based on wages and salaries) in the data set matches that of the Canadian population.
The survey results are compared with other data sources that include: administrative databases, census and other Statistics Canada surveys.
Statistics Canada is prohibited by law from releasing any data that would divulge information obtained under the Statistics Act that relates to any identifiable person, business or organization without the prior knowledge or the consent in writing of that person, business or organization. Various confidentiality rules are applied to all data that are released or published to prevent the publication or disclosure of any information deemed confidential. If necessary, data are suppressed to prevent direct or residual disclosure of identifiable data.
Suppression rules, or data reliability cutoffs, are currently established based on the sample size that underlies the estimate. In general, a sample size of 25 observations is required for the estimate to be published. Depending on the type of estimate, this rule can vary slightly. These rules help protect the confidentiality of survey respondents and ensure the reliability of estimates.
2003 Historical revision:
Every few years, estimates produced by the combined program of the Survey of Labour and Income Dynamics (SLID) and the Survey of Consumer Finances (SCF) undergo a revision. The 2003 revision is the result of three modifications.
1) All estimates, back to 1990, are adjusted to population projections based on the 2001 Census population counts.
2) Starting with 1990 estimates, wages and salaries are benchmarked to the distribution of wages and salaries derived from the T4 statement of remuneration remittance file.
3) The 1992-base low income cut-offs (LICOs) themselves have been revised, resulting from a revision of the 1992 Family Expenditure Survey. SLID and SCF estimates were revised from 1980. Along with the two changes described above, this has an impact on levels of low-income statistics.
There are two types of errors inherent in sample survey data, namely, non-sampling errors and sampling errors. The reliability of survey estimates depends on the combined impact of non-sampling and sampling errors.
Non-sampling errors :
Non-sampling errors generally result from human errors such as simple mistakes, misunderstanding or misinterpretation. The impact of randomly occurring errors over a large number of observations will be minimal. Errors occurring systematically can, on the other hand, have a major impact on the reliability of estimates. Considerable time and effort is invested into reducing non-sampling errors in SLID.
Non-sampling errors may arise from a variety of sources such as coverage, response, non-response and processing errors.
Coverage error arises when sampling frame units do not exactly represent the target population. Units may have been omitted from the sampling frame (under-coverage), or units not in the target population may have been included (overcoverage), or units may have been included more than once (duplicates). Undercoverage represents the most common coverage problem.
Slippage is a measure of survey coverage error. It is defined as the percentage difference between control totals (Census population projections) and weighted sample counts. Slippage rates for household surveys are generally positive because some people that should be enumerated are missed. Slippage rates have been revised back to 1996 using the 2001 Census population projections. In 2003, SLID covered 86.5% of its target population. SLID estimation procedures use Census population projections to compensate for determined slippage.
Rates are also available upon request for sex, province and age groupings.
The cross-sectional response rate was 78.3%.
This overview for the Survey of Labour and Income Dynamics (SLID) provides information on the purpose, content, methodology and products and services pertaining to SLID.
This publication was designed for survey respondents, users of SLID data, researchers and analysts, and individuals who would like to learn more about the survey.