The seventh-wealthiest man in the world, Warren Buffett, turns 90 today. Famously the tycoon/philanthropist pledged to give away 90% of his wealth, founding with Bill and Melinda Gates “The Giving Pledge,” a campaign urging the world’s wealthiest individuals to dedicate the majority of their wealth to giving back. Over $1.2 trillion has now been pledged, with participants including Elon Musk, Ted…