This article is about the funniest parody I’ve read in some time, and makes it mercilessly clear why you can’t just invert protest numbers to determine the number of people who support the status quo.
It’s pretty obvious, by the by, that the numbers of people protesting are important. You can tell, because people who support whatever’s being protested generally aim for the low end of the possible range. Nathan Newman makes an interesting argument against mass protests (link via Electrolite), but I don’t think the math is as simple as he does. A really sizable protest makes it psychologically easier for those who might support the cause but be uncertain of themselves to come out the next time; humans have a lot of herd animal in them. It’d be nice if it were otherwise, and perhaps someday, but right now? Perceptions of numbers matter.
Thus, protestors will always estimate high, and anti-protestors will always estimate low.