According to the Bloomberg Billionaires Index, the wealth of the world's richest person and Tesla CEO Elon Musk decreased by $16.1 billion on October 19th, dropping to $209.6 billion. On the same day, Tesla's stock price fell 9.3%. The previously announced third quarter earnings and revenue did not meet expectations, and quarterly sales fell for the first time this year. After repeatedly lowering car prices, the profit margin fell to its lowest level in more than four years.