Annual Greenhouse, Sod and Nursery Survey
Detailed information for 2002
The purpose of this survey is to collect information on the production and value of greenhouse products, nursery stocks and sod produced in Canada.
Data release - April 25, 2003
- Questionnaire(s) and reporting guide(s)
- Data sources and methodology
- Data accuracy
This survey collects data on greenhouse, sod and nursery operations in Canada. The data are used by federal and provincial agriculture departments and producer associations to perform market trend analysis and to study domestic production with particular interest on imports. This survey also contributes to the Agricultural receipts program of Statistics Canada.
Reference period: January to December of previous year
Collection period: February to March
- Agriculture and food (formerly Agriculture)
- Crops and horticulture
Data sources and methodology
Includes all commercial greenhouse operations as identified every five years through the most recently completed Census of Agriculture.
Specific exclusions from the survey frame are conservatories maintained for non-commercial purposes, institutional farms, farms on Indian reservations, Hutterite colonies as well as operations from the Yukon and Northwest Territories. Cultivated area under glass or plastic that is intended for the production of plants to be set out on the owners' farm is also excluded. The intention is to collect information from farms that produce greenhouse products. For that reason, those establishments that derive their revenues primarily from either the retailing or wholesaling of greenhouse products are excluded from the universe.
The questionnaire was developed by subject matter through consultation with the provinces and industry experts. New questions are not pre-tested in the field. Subject Matter, Survey Operations Division and Operations Research Development Division conduct in-house testing for flow and consistency. Subject Matter will change, add or remove questions as the need arises. Required changes are usually identified through such means Subject Matter research, changes in market trends and field staff debriefing reports.
This is a sample survey.
The survey frame includes all commercial greenhouse growers and all sod or nursery producers. The survey frames are stratified by province and cultivated area. The strata are created in each province on the basis of the square footage of the operation. Up to three strata are created for greenhouses and up to two for sod and nurseries. These strata are determined by the Generalized Sampling System (GSAM). The frame is refreshed every five years with the results emanating from the Census of Agriculture and is maintained in the interim through a process of list collection and verification.
Responding to this survey is mandatory.
Data are collected directly from survey respondents.
The survey information is collected by telephone interview in Statistics Canada Regional Offices, using a Computer Assisted Telephone Interview (CATI) application. Questionnaires are mailed to the farm a few weeks prior to collection for the farmer's reference during the interview.
View the Questionnaire(s) and reporting guide(s) .
With the introduction of the CATI methodology, it is now possible to implement edit procedures at the time of the interview. Computer programmed edit checks in the CATI system inform interviewers during the interview of possible data errors, which can then be corrected immediately by the interviewer and respondent. The CATI system significantly reduces the need for subsequent telephone follow-up, thereby reducing respondent burden and survey processing time.
Erroneous data and partially completed questionnaires are imputed using historical data information.
The survey data collected are weighted within each stratum in order to produce estimates representative of the population. Non-responding units, for example, no contacts and refusals, are dealt with by adjusting the initial sample weights.
Checks on data quality are difficult because similar data are not available elsewhere. The Ontario Greenhouse Vegetable Producers Marketing Board's annual reports provide detailed production information on vegetables in Essex County which confirms the results of the survey in that region.
Analysis of the top contributors and historical comparisons are performed before a final estimate is disseminated.
Statistics Canada is prohibited by law from releasing any information it collects which could identify any person, business, or organization, unless consent has been given by the respondent or as permitted by the Statistics Act. 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.
Revisions and seasonal adjustment
This methodology does not apply to this survey.
The Greenhouse, Sod and Nursery Survey obtains a response rate of approximately 92% of survey respondents. Non-responding units, for example, no contacts and refusals, are dealt with by adjusting the initial sample weights.
The overall quality of the estimates depends on the combined effect of sampling and non-sampling errors. Sampling errors arise because estimates are derived from sample data and not the entire population. Since this survey is a census of all farms, the frame sampling error is not an issue. Non-sampling errors are errors which are not related to sampling and may occur throughout the survey operation for many reasons. For example, non-response is an important source of non-sampling error. Coverage, differences in the interpretation of questions, incorrect information from respondents, mistakes in recording, coding and processing of data are other examples of non-sampling errors.
The estimates published are based on a probability sample of farming operations. The potential error introduced by sampling can be estimated from the sample itself by using a statistical measure called the coefficient of variation (CV). Over repeated surveys, 95 times out of 100, the relative difference between a sample estimate and what should have been obtained from an enumeration of all farming operations with respect to the sample estimates would be less than twice the coefficient of variation. The sample estimate, plus or minus twice the CV is referred to as the confidence interval. For the Greenhouse, Sod and Nursery Survey, CV's at the Canada level range generally from 2% to 10% for the variables that are more frequently reported (area, investment, expenditures, sales) which makes them very reliable. Less commonly reported variables are associated with higher, but still acceptable CV's, usually under 25%.
- Annual Greenhouse, Sod and Nursery Survey