Mark Zuckerberg became the world’s fourth-richest person on Tuesday. “The 31-year-old founder of the largest social network had a $50 billion fortune by the close of regular trading in New York. That vaulted him above America Movil SAB’s Carlos Slim and Amazon.com Inc.’s Jeff Bezos on the Bloomberg Billionaires Index, a daily ranking of the world’s 400 richest people.” Out of the top 10 wealthiest billionaires on Earth, half of them have made their fortunes in technology. (bloomberg.com)