Data for the pig survey is collected by means of web questionnaires or by means of the system to system solution ArgoSofts Winsvin. A sample of about 1.800 holdings with pigs according to the The Central Husbandry Register (CHR) is selected. The survey is a sample survey divided into groups (strata) by the size of pigs and types of pigs on the single holding. Farms with many pigs are selected every time. The answers are validated for unrealistic values and next the sample is extrapolated to the total population of all farms with pigs.
The pig survey is a sample survey, The population includes all active farms in Denmark and is integrated in the Statistical Business Register (ESR) (CHR)[https://chr.fvst.dk], which is kept by Statistics Denmark, and which is registered with pigs in the Central Livestock Register (CHR).
In the selection of the survey population, the holdings are divided into 22 strata according to the types of pigs and the number of pigs in total on the holding obtained by the latest count of pigs from the holding. These data can originate from either the pig survey or The Agricultural and Horticultural Survey depending on which count was the latest for the specific holding.
All farms with at least 5,000 sows and all farms with at least 10,000 pigs for slaughtering or piglets are selected each time, while the selected in other strata are random, however, a holding will at maximum participate 8 consecutive times in the sample.
The size of the sample: - 01 January 2021: 1,827 farms with pigs out of 2,999 farms with pigs - 01 April 2021: 1,799 farms with pigs out of 2,984 farms with pigs - 01 July 2021: 1,735 farms with pigs out of 2,892 farms with pigs - 01 October 2021: 1,716 farms with pigs out of 2,858 farms with pigs
Data are collected quarterly.
Data collection takes place via questionnaires using an electronic reporting form http://www.Virk.dk. Statistics Denmark uploads questionnaires to the respondents, in which they are required to report data to the statistics. Online form and instructions can be found on the information page on https://www.dst.dk (in Danish). Alternatively the system-to-system Agrosoft WinPig.NET.
The statistics go through an validation process. The online reporting ensures that all questions are answered. In the case of on-line reporting, there is a soft validation where the reporters are made aware of values that seem unlikely, so that they can correct them before submission if they are actually incorrect values. In the next phase, the responses received are processed in a database where the reporting is mixed compared with previous periods. Extreme values and large fluctuations are felt. The information is compared with previous reports and information in the central livestock register and corrections are made. However, errors are sometimes corrected only after telephone contact with the farmer. In the last part of the validation, the enumerated figures are examined and extreme developments in the form of large increases or large falls are investigated in more detail.
The statistics on the stock of pigs is a stratified sample census where all farms with pigs according to the Central Livestock Register CHR constitutes the frame population.
These farms are provided with information on the number of pigs and types of pigs from the most recent pig or agricultural and horticultural counts in which the holdings participated. Based on this information, the population is divided into 22 strata. New farms with pigs are placed in their suitable stratum, as are specially selected farms. Farms that have zero pigs according to the latest census information (but are registered with pigs in CHR) are divided into 5 strata, herds with sows are divided into 8 strata, herds with pigs and piglets are divided into 6 strata and finally are ornamental statistics in a separate statute.
When forming the frame population, companies are not included in bankruptcy and suspension of payments. If bankruptcy, suspension of payments etc. after the farm has been selected for the sample, check in the Central Livestock Register (CHR) whether pigs are still on the property. If there are no more pigs on the property, zero pigs will be reported. If there are still pigs on the property, it is assessed individually whether latest data from previous count can be used. If this is not possible, the unit is not included in the list.
The data collected is enumerated for the population. In case of non-response the farm is excluded from the sample and the extrapolation is increased accordingly for stratum where non response occurs. The non-response is about 5-10 per cent.
The data series with the total stock of pigs (pigs, total) are published from 2020 only without seasonal adjustment.