Technology billionaires are making a run for the top of the global wealth rankings as surges for Facebook Inc., Amazon.com Inc. and Google parent Alphabet Inc. added $5.6 billion to their founders’ fortunes this week.

Google co-founders Larry Page and Sergey Brin gained a combined $2.7 billion after the search engine’s ad business reported a growing user base and better cost controls. Jeff Bezos added $1.4 billion on Amazon’s results while Mark Zuckerberg’s net worth rose $1.5 billion after the social networking giant’s second-quarter earnings trounced analysts’ estimates.

Together with Larry Ellison, whose Oracle Corp. announced this week it would buy NetSuite Inc. for $9.3 billion, their combined net worth has risen by 9 percent in 2016. That’s more than double the combined gains recorded this year by the 395 other members of the Bloomberg Billionaires Index.

Zuckerberg has added $7.9 billion to his fortune this year, more than any person on the index, and joins Bezos in a race toward the top of the ranking. At the start of 2015, Zuckerberg was No. 13 on the index with $34.5 billion and Bezos No. 20 with $28.6 billion. Bezos’s fortune soared in 2015 and 2016 and he passed Warren Buffett as the world’s third-richest person on Thursday, having briefly leapfrogged him last week.

These gains are reshaping the dynamic at the top of the index. Four of the world’s 10 richest people have now made their fortunes in technology, up from two — Bill Gates and Ellison — at the start of 2015.