With Microsoft’s share price surging nearly 30 per cent year-to-date, it was all but inevitable that its biggest individual shareholder – former CEO Steve Ballmer – would see his net worth skyrocket too.

On Monday, Steve Ballmer overtook Bill Gates to become the sixth-richest person in the world.

Ballmer owns an estimated 333.25 million shares — or around 4 per cent — of Microsoft, while its co-founder Gates has 102.99 million shares, according to SEC filings.

More than 90 per cent of Ballmer’s A$235.75 billion net worth is by way of his Microsoft shareholding, according to the Bloomberg Billionaires Index.

Apart from Microsoft, Ballmer also bought the NBA’s Los Angeles Clippers for A$3 billion in 2014. That investment is estimated to be currently worth around A$6.9 billion.

Gates has diversified his A$235 billion fortune. Approximately half his wealth is held through Cascade Investment, which was created with the proceeds of Microsoft stock sales and dividends.

He also owns a A$31.49 billion stake in waste-management company Republic Services through Cascade.

After Gates co-founded Microsoft in 1975 and led it until 2000, Ballmer replaced him as CEO. Ballmer retired in 2014, the same year that he became Microsoft’s largest shareholder.

Both billionaires have different approaches to how they approach philanthropy. Gates along with his ex-wife Melinda French Gates and fellow-billionaire investor Warren Buffett has spent billions from his own wealth to build the A$112.47 billion Gates Foundation which is reported to be one of the world’s biggest charitable organisations.

Gates, Buffett and French Gates also founded The Giving Pledge which encourages the world’s wealthiest individuals to give away the majority of their fortunes during their lifetimes, or in their wills, to philanthropic causes. Ballmer is not a signatory to The Giving Pledge, while his own philanthropic contributions pale in comparison to Gates.

Microsoft’s share price has surged this year as its current CEO Satya Nadella has unveiled an ambitious roadmap to push out AI capabilities across notebooks from several manufacturers this year.