Forbes unveils tech billionaires

Share price volatility ensured not all the world's top tech tycoons saw their net worth increase over past 12 months

Ninety of the world's dollar billionaires made their fortune in technology, according to Forbes' 2012 Rich List, although falling share prices have hit the pockets of some high-profile entrants including Larry Ellison.

Microsoft founder Bill Gates was pipped to the top spot for a third year by Carlos Slim but is closing in on the Mexican telecoms magnate after his worth rose by $5bn (£3.2bn) to $61bn.

Larry Ellison (pictured) fell one place in the rankings to sixth after a 15 per cent year-on-year drop in Oracle's share price knocked $3.5bn off his fortunes.

In total, there were 1,226 dollar billionaires, with a combined worth of a record $4.6tn, Forbes said. Real estate magnate Gerald Cavendish Grosvenor was the highest-ranked Brit, with his $11bn fortune placing him in 78th spot.

The number of tech billionaires rose from 89 to 90 year on year.

Google founders Sergey Brin and Larry Page tied for 24th despite seeing their fortunes drop by more than $1bn to $18.7bn.

Amazon founder Jeff Bezos is $300m richer thanks to a slight rise in Amazon's stock since the 2011 list was compiled. Last autumn his firm launched its "iPad-killing" tablet, the Kindle Fire, and now sells more e-books than the paper variety.

Facebook supremo Mark Zuckerberg was among the biggest gainers after a $4bn spike in his worth to $17.5bn propelled him up eight places to 27th.

Michael Dell, whom Forbes dubbed as the "original dorm room entrepreneur", saw his fortune rise by $1.3bn to $15.9bn on the back of an 18 per cent year-on-year rise in Dell's share price. Steve Ballmer saw his net worth rise by $1.4bn to $15.7bn.