Due to UK's high taxes and his state taxes in California.
http://www.thepostgame.com/blog/dish/201307/phil-mickelson-british-open-taxes
http://www.thepostgame.com/blog/dish/201307/phil-mickelson-british-open-taxes
Makes no sense for him to stay in California, but if he's dumb enough to stay, and can afford it, I guess that's his right.
900000$ in taxes in one week is a big hit no matter how you look at it
ea, I thought he was in Scottsdale, Arizona, but of course I don't know their tax laws either. He won the Tourney a week before as well, so he may still get upwards of $800k.