The census is important for all with hearing loss as it allows identification of need and support, The UK made a mess of forcing through a question to identify deaf and cultural people, because they were non-specific about WHO they wanted to Identify.
The result was huge negative for the sign users as prior to the census it was claimed at that time by sign charities over 50,000 deaf used sign language in the UK, the census results did not agree, it revealed less than 15,000 and even that was challenged because the question asked was not specific to daily usage or reliance just 'do you know sign language?' This meant hearing terps were allowed, family members, friends, and learners to be included alongside actual deaf users and the question wide-open to misrepresentation.
Of course, as the state was concerned it suggested there was no great demand for it, and charities suffered lower funding! Opponents of BSL suggested the 'Deaf' had deliberately 'loaded' the question on the census by inferring by default, 'deaf' and 'Deaf' were one and the same, assured in the state's ignorance of the D/d thing, or the challenges made to it by various other hearing loss and deaf areas.
It failed spectacularly because BSL is not a feature of HoH communication, and relative BSL activist areas were determined to make the point, so it was a real own goal for the UK BSL people. The true test of sign language need is to identify reliant and daily users, many many attempts have been made by activists (By ATR itself), and by charities dedicated to hearing loss to do this, and we all have failed, defeated by the UK's data protection act which bans any identification of the BSL user this way.
The current situation is 'think of a number' double it etc, because nobody knows, so nobody can challenge. Currently, 12m have a hearing loss here and 150,000 use BSL are being claimed, we are in the realms of fantasy in many respects which supports areas that want funds, but the funding is not coming through too many have cried wolf too often.