Then catch data is like polling. It's a picture of what happened in the past. It doesn't necessarily tell you what's going to happen in the future. It may tell you the governing party is declining in popularity, but it doesn't predict with accuracy what's going to happen in the next election.
It's sort of like that. It's self-reported, for the most part. It's the catch data of fishermen on what they caught this year, last year and the year before. Is that correct?