I dont use the alexa toolbar nor would I ever install it. But, I have a
few questions about it.

They rank webpages. The data they collect to rank a page only comes from
people who use the toolbar, correct?

So, lets say I have a webpage that ranks 75,000 in alexa, but I know my
users aren't the type to run the alexa toolbar. Is it safe to assume
that my page may actually be more popular than 75,000?