That's part of the difficulty. We really don't know. It's a combination of factors, obviously. I have a daughter with three children under the age of 2, all in diapers. There are days when she can't brush her teeth. She has a neighbour with one daughter who is nine years old. Which of those two, given the voluntary survey, is more likely to be inclined to fill it out? I think there will be a clear bias in favour of people who have time, who are motivated, who see some benefit to the data coming from this, and who are perhaps civic-minded and law-abiding citizens.
Unfortunately, governments at all levels make policy decisions not just for the law-abiding citizens who drive under the speed limit and don't litter but for all of society, including those who exceed the speed limit.