The Vanguard Morningstar Mega Cap Growth ETF (NYSEMKT: MGK) has delivered a compound annual return of 13.6% since its 2007 launch, outrunning the S&P 500's 10.9% annual average over the same period. The complication is structural: more than 72% of the fund's assets sit in technology, and three stocks account for 36.2% of everything.
What's driving the performance
The fund tracks the Morningstar U.S. Mega Cap Growth index, which holds 56 of the most valuable companies listed on American exchanges. Nvidia holds the top position at 13.52% of the portfolio, followed by Apple at 13.19% and Microsoft at 9.49%, as of July 31. Nvidia's weighting reflects what has happened to the business: from a $360 billion company at the start of 2023, the chipmaker's stock rose 1,370% over the three and a half years that followed, as demand for its data center graphics processing units accelerated across AI training and inference workloads. Microsoft and Apple each more than doubled in value since early 2023, slightly outpacing the S&P 500, though both entered that period already among the world's largest companies.
The unit economics of this structure are legible. The fund's 13.6% annual rate against the S&P 500's 10.9% translates into real dollar differences at scale. Vanguard's own projections, applying those historical rates, show a 35-year-old investor placing $30,000 in MGK reaching $1,375,533 by retirement age, against $668,448 from the same amount in an S&P 500 fund. The quarterly rebalance of the underlying index means companies no longer meeting the index's criteria get replaced, which limits the risk of a failing position sitting on the books indefinitely.
The counterargument
The counterargument deserves its own reckoning. A fund where three positions represent over a third of all assets is a concentrated technology trade, not a conventional diversified index product. The read-through is that Nvidia's pricing power in the GPU market, supported by persistent supply shortages and AI infrastructure spending, has contributed a significant share of recent alpha. If that spending cycle slows, or competition narrows those pricing advantages, the 2.7-percentage-point annual gap separating MGK from the broader index could compress quickly. Vanguard's own materials note that past performance is not always a reliable guide to future results. That caveat carries more weight here than it does for a 500-stock fund.
On balance, the case for MGK rests on a clear thesis: the companies capturing the fastest-growing revenue pools in technology tend to stay in the index, while laggards rotate out. The line to watch is whether AI infrastructure spending sustains the pricing conditions that produced Nvidia's 1,370% return. That figure is not a feature of the fund's design. It is the residue of a specific technology cycle, and the next one may not be as generous.