The graph isn’t accounting for groups which disbanded before the 2020 survey, because we don’t have direct access to how many groups came into existence and then stopped existing before the survey (although we do have good information about this for recent years, since CEA are aware of almost every active group (I assume- it seems unlikely there are a lot of secret groups)).
That said, as discussed here, when we compare cross year data, we don’t see evidence of much attrition on a yearly basis.
The graph isn’t accounting for groups which disbanded before the 2020 survey, because we don’t have direct access to how many groups came into existence and then stopped existing before the survey (although we do have good information about this for recent years, since CEA are aware of almost every active group (I assume- it seems unlikely there are a lot of secret groups)).
That said, as discussed here, when we compare cross year data, we don’t see evidence of much attrition on a yearly basis.