New Delhi, April 2 -- It's perhaps no surprise that stock market volatility is reflected in the ranks of the world's top billionaires so far this year.

Tech billionaires still dominate the Bloomberg Billionaire Index, led by Tesla CEO Elon Musk. Musk's net worth-at $644 billion by Bloomberg's calculations-is set to skyrocket further, potentially reaching at least $1 trillion with the initial public offering of SpaceX, the trillion dollar space exploration company he founded and leads. The IPO, filed confidentially on Wednesday with the Securities and Exchange Commission, is expected to raise between $40 billion and $80 billion.

Two sons of Walmart founder Sam Walton-Jim Walton, co-manager of the family office and holding company Walton ...