If you would like to understand the methodology behind these surveys, you should read Dr. Ewing's article; it is worth your time. He also responds to member concerns here:
...ACS members have also asked specifically about the decline in the response rates for each survey. Although the drop has been observed for some time, it has accelerated in recent years. For example, the Comprehensive Survey response rate of 36% in 2011 dropped to 28% in 2014. Though disconcerting, the decline in response rates is a general trend for surveys in all segments and not unique to ACS. The increased prevalence of surveys has resulted in ambivalence, which makes it tougher to convince individuals to take the time to reply...While I understand that this is a problem of resources (we can't send people to ACS members' houses, knocking on their door and asking them to fill out the ChemCensus), I am a little bit concerned that CEPA apparently does not have a plan or an answer to the response rate problem.
If the response rate continues to fall, at what point does the data from the ChemCensus or the annual Salary Survey become less valuable? What others plans does CEPA have to raise the response rate? (I have gotten physical postcards, reminding me to fill out my Survey (and I do!)) What distinguishes respondents from those who do not respond? I am sure that CEPA is looking at these questions, and I look forward to the answers.