NEW YORK — Holiday shopping has already made the season merry for Amazon founder Jeff Bezos.

Investor optimism about sales at the online leader has sent its stock up 58 percent so far year, and 5 percent in just this past week. The 81 million shares Bezos owned according to documents filed in April are worth $96 billion at Friday’s closing price. Bezos also owns The Washington Post through a holding company.

Bloomberg News said that Bezos has broken the $100 billion mark in wealth — the first time a billionaire surpassed that mark since Microsoft co-founder Bill Gates did it in 1999.

Analysts at Bain expect Amazon to take half of the holiday season’s sales growth this year.