• The Baron Partners Fund, managed by Ron Baron, has outperformed the market in December.
• Tesla is the largest holding and is up 34% this month.
• Baron is BI's Investor of the Month for December.

Thanks to his considerable bets on Elon Musk, investing legend Ron Baron is BI's Investor of the Month for December.

His Baron Partners Fund (BPTRX), which he co-manages with his son Michael Baron, was up 15% month-to-date as of December 24, while the broader market was flat. Year-to-date, it had risen 37% versus the S&P 500's 27%.

Electric vehicle maker Tesla (TSLA), led by Elon Musk, has been the biggest publicly listed contributor to the fund's outperformance. It's the most prominent holding, at 33.4%, and is up 34% this month.

The fund's second-largest holding, SpaceX, has also pitched in meaningfully at an 11.1% weighting. The Musk-run space exploration and satellite firm is privately held, but numbers from a liquidity event earlier this month, during which investors cashed out of their shares, showed the firm's implied valuation grew by 65% to roughly $350 billion. According to a memo cited by Bloomberg, shares sold at $185 each, compared to $112 "less than three months ago."

At the 31st Annual Baron Investment Conference on November 15, Baron said he remains uber-bullish on Tesla and SpaceX in the years ahead.

"Tesla, we invested $400 million between 2014 and 2016, and made $6 billion in profits so far. And I think we're gonna make four or five times again," he said.

"SpaceX, since 2017, made seven-times our money so far," he continued, adding that he sees his investment growing another 15 times over the next 15 years from November's levels.

Baron's support for Musk's firms is well known, and Musk spoke at the 29th Annual Baron Investment Conference in 2022. Tesla and SpaceX are also top holdings in the Baron Focused Growth Fund (BFGIX) and the Baron WealthBuilder Fund (BWBFX).

After Tesla and SpaceX in the Partners Fund, its next largest holdings are Arch Capital Group (ACGL) at 9.6%, CoStar Group (CSGP) at 7.3%, and Hyatt Hotels (H) at 6.8%. Performance has stagnated for each of these stocks over the last month, however.

Beyond its returns this year, the Partners Fund has also performed impressively over the long term. It's beaten 99% of large-cap growth funds over the last five-, 10-, and 15-year periods, according to Morningstar data.

Those considered for BI's Investor of the Month include: managers of US-listed mutual funds or ETFs, those whose funds have outperformed peers in a given month, and those whose funds are outperforming a benchmark index (in most cases this will be the S&P 500) on a trailing 12-month basis. Leveraged funds are not considered.