Gautam Adani's net worth has dipped by $12 billion to $66.8 billion this year so far, according to Bloomberg's Billionaires Index. It's the largest wealth erosion this year after Tesla CEO Elon Musk, whose net worth eroded by $35.2 billion to $397 billion. The decline in Adani's wealth comes as shares of Adani Group firms fell amid broader market downturn.