A history information anonymization method includes an association step of associating each of a plurality of pieces of history information collected from a plurality of TVs in a current cycle with a temporary ID associated with a TV at a collection destination; a grouping step of getting together a plurality of IDs into a plurality of groups such that for the IDs in each group, contents of history information associated in the current cycle and in a past cycle are identical; an anonymity judgment step of judging whether each of the plurality of groups satisfies anonymity; and an ID changing step of changing only some of the plurality of temporary IDs associated with the plurality of TVs, when it is judged that any of the plurality of groups does not satisfy anonymity.
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