Prices indices may be revised in the months following their first publication.
This is especially the case for cows milk price. As it is collected with a lag of one month, the most recent month price is imputed using the previous month's price and the seasonal adjustment coefficients. The month after, a then collected price replaces the imputed one and is used to impute the price of the most recent month. The comments of the cows milk price index changes do not concern the imputed value but the last collected value. For example, in February, the January price is imputed from the December price and it is the latter which is the subject of a comment.
Some product prices are set for periods of 12 consecutive months. They are called "prix de campagne". It concerns, for instance, sugar beet, ewe's milk, cereal seed or potatoes for starch extraction. Until updated data are available, campaign prices are extended at the same level. At the time of the update, from 12 to 24 monthly prices may be revised.