Documentation of statistics: Cereal Prices used for Regulation of Land Rents
Normally the same firm from last years survey are selected, men periodically, every third or fourth year, new firms might be added from the industry "Wholesale of cereals and feeding stuffs", industry code 46.002 according to the industry classification DB07.
https://www.dst.dk/en/Statistik/dokumentation/documentationofstatistics/cereal-prices-used-for-regulation-of-land-rents
Documentation of statistics