This chart shows the activity of Top Brokers in Marin County.
This chart reflects Market Share in $ volume. 
GMAC here is Pacific Union which was recently sold. 
If you view the Pacific Union vs. Alain Pinel post below
you'll see that Pacific Union is in "transition" right now. 

This chart reflects market share in UNITS SOLD


This Data reflects sales from January 1, 2008 to December 31, 2008