Pay depends enormously on the local market for your skills. NYC and Boston pay almost as much as Mountain View, while (ex) London pays much less. People moving between offices are often offered large increases/decreases. A strategy of joining in Mountain View and then transferring to a lower-paying office isn't generally going to give you much higher pay at the new office (though you'll of course have the money you put away while in Mountain View).
(Speaking only for myself)
I think it's about half.
> is it possible to move to say Boulder within Google easily?
Reasonably. You need to find a team at the other office that has openings for someone with your skills, but I know many people who have done it (Mountain View -> Cambridge, NYC -> Seattle, Cambridge -> Pittsburgh, Mountain View -> Boulder among others).
https://about.google/locations/?region=asia-pacific&office=s...
Does anyone know what proportion of their workforce is not in California?
A question to Googlers and those who have worked there, is it possible to move to say Boulder within Google easily?