Volatile stock markets, cratering oil prices and a stronger dollar led to a dynamic reshuffling of wealth around the globe and a drop in ten-figure fortunes for the first time since 2009. For our 30th annual guide to the world’s richest, we found 1,810 billionaires, down from a record 1,826 a year ago. Their aggregate net worth was $6.48 trillion, $570 billion less than last year.  It was also the first time since 2010 that the average net worth of a billionaire dropped – it is now $3.6 billion, $300 million less than last year.