LNKI. What are the questions regarding deaf people and sign usage? degree of skills? daily or occasional usage etc? In the UK census a simple question was do you sign and it failed to identify who did, or how effective it was for the deaf, the question was 'loaded' by signing activist language groups to omit actual usage and reliance facts.
It meant a census statistic later released showed deaf claims to be false on BSL use/need or deaf attainment of it. I am assuming USA deaf were consulted on exactly what questions are asked and with detail?