6. Accuracy and reliability |
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6.1. Accuracy - overall |
The Job Vacancy Survey is a sample survey which inevitably involves uncertainty, which increases with more breakdown of the data. To counteract this uncertainty, participant answers are weighted by their sample probabilities based on the size and economic activity of legal entities to adjust the sample to the population. |
6.2. Sampling error |
Data is collected using a stratified random sample of all legal entities that had more than one employee working for them on average during each month of the calendar year. Stratified random sampling is used to minimize sampling error and ensures that each subgroup within the population receives proper representation within the sample. Nevertheless, some uncertainty can always be expected when using sample surveys since the sample can never be an exact replica of the population. This uncertainty increases with more breakdown of the data. To inform users of this uncertainty, 95% confidence intervals are published in the quarterly news releases. |
6.2.1. Sampling error - indicators |
Coefficient of variation (taking into account the sampling design) or estimated sampling error for the number of job vacancies (see guidelines). |
95% Confidence intervals (in brackets) of number of vacant job positions: 1st quarter 2022: 6,440 (4,880-8,000) 2nd quarter 2022: 12,240 (9,280-15,200) 3rd quarter 2022: 8,790 (7,150-10,440) 4th quarter 2022: 6,220 (4,990-7,450) Coefficient of variation (Standard error/Number of vacant job positions) 1st quarter of 2022: 12.3 2nd quarter of 2022: 12.3 3rd quarter of 2022: 9.6 4th quarter of 2022: 9.9 |
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6.3. Non-sampling error |
Information on variables with non-negligible measurement and processing errors |
Information on main sources of (non-negligible) measurement and processing errors and, if available, on methods applied for correction |
Estimation bias: An assessment of the non-sampling errors, in terms of the absolute number of vacant posts, for the total number of job vacancies and, where possible, for aggregation level of NACE Rev. 2 specified in Annex 1 to this Regulation and size classes (1-9, 10 + employees). |
Remarks |
Not applicable |
Not applicable |
Not applicable |
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6.3.1. Coverage error |
Description of any difference between the reference population and the study population |
Description of classification errors |
Description of any difference between the reference dates and the reference quarter |
Any other relevant information |
Not applicable |
Not applicable |
Not applicable |
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6.3.1.1. Over-coverage - rate |
Not available. |
6.3.1.2. Common units - proportion |
The number of vacant jobs is obtained from the survey and the number of occupied jobs is obtained from register data. |
6.3.2. Measurement error |
Like with all data collected from a sample of the population, measurement errors can cause bias in estimates. The main sources of measurement errors that could be found in the JVS are errors that stem from the questionnaire used and mistakes in the data processing. Errors due to the questionnaire used can arise from the questionnaire design and question wordings for example. To minimize possible effects from the questionnaire, all possible question-wording effects were kept in mind when the items were written and all concepts that the questionnaire is intended to measure were clear. The questionnaire was also pre-tested before it was put in use. Respondents can contact Statistics Iceland with questions regarding the questionnaire if problems with interpretation arise. Errors in the data processing are minimized by using the statistical software R studio, where the history of all changes to the data processing script is available. That way, it is easy to backtrack all results if issues are found. |
6.3.3. Non response error |
The non-response rate in the Job Vacancy survey is really low as legal entities have legal obligations to return the requested data to Statistics Iceland. |
6.3.3.1. Unit non-response - rate |
Unit response rate |
The unit non-response rate for 2022 was: 8.0% for the 1st quarter 1.6% for the 2nd quarter 0.9% for the 3rd quarter 0.4% for the 4th quarter |
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6.3.3.2. Item non-response - rate |
The item non-response rate for 2022 was 0 for all quarters. |
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6.3.4. Processing error |
Not applicable. |
6.3.4.1. Imputation - rate |
Item imputation rate and methods and, where possible, the effect of imputation on the estimates for the variables transmitted |
No imputation was performed on the results from 2022. |
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6.3.5. Model assumption error |
If modelling is used, include a description of the models used. Particular emphasis should be given to models for imputation or grossing-up to correct for unit non-response. |
Not applicable. |
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6.4. Seasonal adjustment |
Brief description of seasonal adjustment procedures, in particular with regard to the European Statistical System guidelines on seasonal adjustment which have been endorsed and supported by the SPC. |
Not applicable. |
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6.5. Data revision - policy |
Statistics Iceland revision policy can be found in the following link: Revision policy |
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6.6. Data revision - practice |
Provide a revision history, including the revisions in the published number of job vacancies and a summary of the reasons for the revisions. |
Number of vacant jobs The population numbers for the weights to calculate number of occupied jobs are fixed when one year has passed from the reference year. Until then, a little fluctuation might be seen in the figures due to updated and better information in the business register. Number of occupied jobs In the third quarter of 2021, changes were made to the methodology of the Job Vacancy Survey. In order to increase the reliability of information on the number of occupied jobs, the number of employees in the reference quarter is now obtained from the pay-as-you-earn registry, instead of using point estimates from the IS-JVS. At the time of change in the methodology, the whole time series was updated in accordance with the revised method. The register data of number of occupied jobs is constantly revised and updated. To minimize unnecessary fluctuation and changes in the time-series, figures about occupied jobs are fixed when twelve months have passed from the reference period of the results. Statistics Iceland then intends to revise the figures every three years if any remarkable changes are seen in older figures. |
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6.6.1. Data revision - average size |
Not available. |