Back in 2010 the world's billionaires boasted a combined net worth of $3.6 trillion (£2.8trn). This year the figure has jumped to $8.7 trillion (£6.8trn). While some of the global mega-wealthy have seen their fortunes decline since 2010, others have accumulated bewildering sums of money. Comparing the Forbes Billionaires lists from 2010 and 2019, we reveal the people who've garnered the most dough over the past decade.