I can tell you, based on the fact that I do voluntary surveys in Saskatoon and in our region on a regular basis, that it is not the same. Depending on the audience I speak to, even using the authority of the health region and my office as medical officer, with repeated follow-ups with individuals I cannot approach the level of compliance that the mandatory census gives me with data, even when I'm collecting locally and people know me and how I'm using the data.
The reality is, people like that, who you mentioned, are inundated with voluntary surveys on a regular basis, and that's becoming more the norm. The fact that it's voluntary means it's no different and it gets put into the garbage.