In 2015, Facebook (META 0.20%) CEO Mark Zuckerberg continued to turn his billions of dollars of net worth into more billions. But he also announced a mind-boggling commitment to give nearly all of his fortune away. Here's how his wealth increased during the year and a look at his ambitious philanthropic aspirations.

Zuckerberg (right) at Facebook headquarters. Image source: Facebook.

Facebook stock gives Zuckerberg's billions a lift
During 2015, the self-made billionaire's 33% boost to his net worth, from approximately $34 billion at the end of 2014 to $46 billion at the time of this writing, was driven by Facebook's rising stock price during this period. The majority of Facebook's net worth is "derived from his 15 percent stake in Facebook," according to the Bloomberg Billionaires Index. 

The rise in Facebook's share price during this time was driven by Facebook's continued rapid growth during 2015.

While Facebook has yet to report its fourth-quarter results, its traling-12-month performance highlights how well the company is doing recently. Revenue during this period compared to the year-ago period is up a whopping 42.3%. And even in the company's most recent quarter the social network has maintained high year-over-year revenue growth of 40.5%.

And unlike many growth companies, which fail to grow net income meaningfully as spending on expansion initiatives weigh on profitability, Facebook is also growing its net income to impressive levels. During Q3 alone, for instance, the social network's quarterly net income reached $892 million -- or $1.6 billion when excluding the amortization of intangible assets, share-based compensation, and related payroll tax expenses. This compares to $806 million in net income during the year-ago period, or $1.1 billion on a non-GAAP basis.

But an improving bottom line isn't the only metric Facebook investors are excited about. Rapid growth in Facebook's social platforms' user bases suggests there's plenty of opportunity for more business growth over the long haul. Facebook, Facebook Groups, Messenger, WhatsApp, and Instagram now boast more than 1.55 billion, 925 million, 700 million, 900 million, and 400 million monthly active users, respectively.

Mark Zuckerberg and his wife, Dr. Priscilla Chan, have committed to giving away 99% of their wealth during their lifetimes. Image source: Facebook.

Zuckerberg sets a new charitable standard
This year also goes down in history as the year Zuckerberg and his wife set a new standard for billionaire giving. The couple announced they would give away 99% of their Facebook shares throughout their lives, starting with "no more than $1 billion of Facebook stock each year for the next three years," according to a Facebook SEC filing. Billionaire Warren Buffett has made a similar pledge, promising in 2006 to give more than 99% of his wealth to philanthropy during his lifetime or at death. But what marks Zuckerberg's philanthropy as a new standard is the fact that he is beginning this ambitious giving at the age of 31.

Notably, if Facebook continues to give less than $1 billion away each year, and if the social network's shares continue to appreciate, the CEO may need to increase the rate of his annual philanthropy in order to give away 99% of his wealth during his lifetime.