There is one thing about Mark Zuckerberg that has never changed since he launched Facebook and became one of the youngest billionaires in the world: the grey T-shirt he wears every day.

The Facebook CEO shared a picture of his wardrobe and the two types of t-shirts he wears every day this week as he returned to work following his paternity leave.

His bland outfits may seem dull, but Zuckerberg has a legitimate reason for donning the same T-shirt every day. He claims dressing in the same way allows him to focus his energy on more important decisions at work.

First day back after paternity leave. What should I wear? Posted by Mark Zuckerberg on Monday, 25 January 2016

The 31-year-old explained this during his first public question and answer session in 2014 when an audience member asked why his outfits never changed. “I really want to clear my life to make it so that I have to make as few decisions as possible about anything except how to best serve this community,” said Zuckerberg.

“I'm in this really lucky position, where I get to wake up every day and help serve more than a billion people. And I feel like I'm not doing my job if I spend any of my energy on things that are silly or frivolous about my life.”

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