Ron Baron — a longtime Elon Musk investor and a newcomer to the exchange-traded fund universe — is already subverting norms in the $14tn industry.A peek under the hood of the Baron First Principles ETF (which trades under the ticker RONB) reveals a portfolio that, depending on the day, many thought to be impossible: One of its largest holding is SpaceX, a Musk-founded privately held rocket company, with a weighting that has vacillated between 11% and 22% in the past few weeks.The stake often exceeds the 15% ceiling on illiquid assets that US regulations put in place for open-ended funds — a category that includes non-public equities.The reason why Baron Capital is able to do so boils down to a little-known fact about how issuers report their holdings to the Securities and Exchange Commission: Fund firms determine the liquidity classifications of their holdings themselves, rather than US regulators doing so. While “illiquid” securities are capped at the 15% threshold, the other three categories — highly, moderately and less liquid — do not have percentage limits, according to Bloomberg Intelligence. Indeed, Baron Capital is classifying its SpaceX holding in RONB as “less liquid”, a spokesperson confirmed.The RONB episode is blurring the traditionally held boundaries of the ETF wrapper. While the vehicle has expanded to markets such as commodities and cryptocurrencies, the lion’s share of the industry’s assets are concentrated in ETFs that hold publicly listed stocks and bonds. The introduction of private equity and credit has fanned fears about a liquidity mismatch between the underlying holdings and the ETFs themselves, which trade continuously throughout the day. Additionally, there are outstanding questions about how private securities are being classified — for example, while RONB may regard SpaceX shares as “less liquid” securities, other fund managers may treat them differently.“If you’re going to be a new entrant, maybe making a splash is a good thing — thinking from their perspective, it’s a competitive marketplace and how do you stand out? Certainly this makes it stand out, for better or worse,” said Adam Sabban, Associate Director, Equity Strategies at Morningstar. “Having such a large stake in privates is rare, particularly when it’s mostly in one company. Most funds are afraid to bet 15% on any stock, let alone a privately held one.”Baron Capital has been investing in SpaceX in its funds since 2017, and informed the SEC of its plan to classify the shares as “less liquid” given its history of transacting in the stock, according to a person familiar with the matter.RONB is among just a handful of ETFs that hold private assets, though its exposure is by far the largest percentage weighting. The full list includes the $1.7bn ERShares Private-Public Crossover ETF (XOVR), which has a nearly 10% allocation to SpaceX through a special- purpose vehicle. Meanwhile, funds such as the $500mn SPDR SSGA IG Public & Private Credit ETF (PRIV) devote a sliver of their portfolio to private debt.While Baron Capital is new to ETFs, the bottoms-up stockpicking firm has cultivated a loyal following among its mutual fund investors since its founding in 1982. The asset manager is known for its early bets on Musk’s companies, which helped the Baron Partners Fund clinch the title of being the sole actively managed mutual fund to outperform the Nasdaq 100 over the five, 10 and 15 years through July 2023, according to Bloomberg Intelligence.Leaning heavily into private companies such as SpaceX — which is combining with xAI into a larger entity in a deal valued at $1.25tn as it reportedly looks to go public later this year — could help RONB become “the next active ETF star,” Bloomberg Intelligence senior ETF analyst Eric Balchunas wrote in a recent report. While the fund has fallen on a total return basis since its mid-December launch, investors have bought in nevertheless. Nearly $100mn has flowed into RONB so far in 2026, bringing its total assets to $161mn.However, those inflows have exposed a key drawback of private company-heavy ETFs: More money can lead to temporary dilution, given that private shares are more difficult to acquire than public stocks. The opposite is true with outflows: When faced with redemptions, its allocation to SpaceX may increase as the fund sells its more liquid holdings. In the case of RONB, while its SpaceX stake currently sits at about 18%, it stood at nearly 22% two weeks ago, data compiled by Bloomberg show.“Creations and redemptions are being handled through liquid assets, though it does mean private positions can be diluted over time as the fund grows, which is a trade-off investors need to understand,” said Bloomberg Intelligence mutual fund analyst David Cohne.Baron Capital’s move to classify SpaceX as “less liquid” in order to bypass the 15% cap has yet to inspire copycats. While it may be that the “definition of illiquid is changing,” according to Ark Investment Management’s Cathie Wood, her firm opted to go with the interval fund format to invest in private companies in order to exceed that threshold. The ARK Venture Fund counts private companies SpaceX, Figure AI and OpenAI among its top holdings.Additionally, Ark has found that the executives of the private companies that the firm invests in have been reluctant to have their shares included in highly liquid ETFs, according to Wood.“We have actually gone to some of our private companies, the one in the interval fund, saying ‘Hey, we would love to add you into our ETFs because we think this is such an important story’,” Wood said on Bloomberg Television’s ETF IQ. “We found over time that they have been reticent.”
