Warren Buffett's annual letter provided an inside look at the health of the businesses that comprise Berkshire Hathaway(BRK) , as well as some insight on the political campaign. Buffett's stock fell 12% in 2015, underperforming the stock market, but Berkshire Hathaway's book value increased and profit improved at several Berkshire companies, except for insurance. Profit for the company overall topped $24-billion in 2015. Buffett said in his letter that improvements at BNSF were the most important development in 2015. Buffett also weighed in on the political campaign, pointing to a 'negative drumbeat' of discourse. Buffett has already come out in support of Hillary Clinton. Buffett also talked about how he was finally embracing the 21st century, by deciding to webcast the Berkshire Hathaway annual meeting this spring. Buffett said shareholders will be able to make sure he and his partner, Charlie Munger, don't drift off into 'la-la land' during the meeting.