Zara king boosts fortune by $9b in 2013

The world's 300 richest people added $524 million to their bank accounts, the December 31st Bloomberg Billionaires Index update shows.

That puts their combined wealth at a cool $3.7 trillion. 

Former Microsoft chief Bill Gates clocked up the biggest gains in 2013 with his wealth pile growing $15.8 billion to $75.8 billion on the back of rising Microsoft shares. He also snatched back the number one position in the Bloomberg rich list, overtaking Mexican tycoon Carlos Slim.

Spain's Amancio remains in third place. The low-key billionaire's wealth increased by almost $9 billion to $66.4 billion after his fashion empire which includes the clothing chain Zara grew 14 percent in 2013.

SEE ALSO: The Local's in-depth profile of Amancio Ortega, the richest man you've never heard of

Ortega's daughter Sandra sits in 180th place in the Bloomberg list with a fortune estimated at $7.2 billion.

Also appearing on the list in 10th place is Sheldon Adelson, the founder of casino giant Las Vegas Sands Corp.

Adelson made headlines in Spain recently when he backed away from plans to build the €30-billion Eurovegas megacasino project on the outskirts of Madrid. He added $14.4 billion to his net wealth in 2013 with company shares up 71 percent.

The average age of Bloomberg's billionaires is 67 while the youngest on the list is 29-year-old Facebook founder Mark Zuckerberg. 

There are just 11 women among the top hundred billionaires listed by Bloomberg.