In an earlier thread I pointed out the same thing. What I eventually realized was that many of my old pages didn’t use my main template, which included the Google javascript. Mint, on the other hand, was automatically inserted into every viewed page using the prepend script provided in the Mint install.
Shaun suggested adding the Google javascript to the Mint script — and the immediate result was that my Google and Mint numbers became very close for several months. Search this forum for my posts, or for Google Analytics, to find the instructions.
Unfortunately, since a recent server crash and subsequent changes made by my ISP to my server, Google is now much higher. We still haven’t determined what’s causing that…