New Listing, No History: Estimating the Risk of an IPO
SpaceX listed last week, the first of a possible wave of megacap IPOs. The index effect may be smaller than headlines imply. Under conservative free-float assumptions, the largest candidates would add less than 1.5% combined weight to the MSCI USA Index.1
A discretionary fund is a different matter. In a concentrated sector or thematic strategy, stock-specific and factor risks such as momentum and volatility can dominate. A new listing's risk impact starts on day one, yet the stock has no return history.
Model design can bridge the missing history. A fundamental, cross-sectional risk model derives exposures from observable characteristics rather than regressions on the stock's own returns. A new listing carries industry and fundamental exposures immediately.2 Stock-specific risk, momentum and volatility, however, are built from price history. The latest MSCI Global Equity Factor Model (EFMGEMLT) fills these with information from elsewhere.
The model estimates specific risk from similarly-sized peers and the stock's own short return window. Residual volatility initializes near the sector 85th percentile, decaying as live returns accumulate. Momentum is computed from excess returns over a trailing 252-day window with a 126-day half-life. For a new listing, the missing history is filled with market returns. The stock opens neutral, and live returns enter within two weeks.
Two recent offerings show this in practice. CoreWeave listed in March 2025, and Figma shortly after. Factor exposures across model generations diverged most in the first weeks of trading, as did stock-specific risk. Within 120 days, as return history accumulated, the forecasts converged.
For a risk manager, the difference was immediate. The enhanced IPO treatment produced estimates that started near where both models finished.
Style factor exposures from listing date. Discrete steps occur as descriptor estimation windows reach required length.
Forecast specific risk from listing date through first 220 trading days.
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What the SpaceX IPO Means for Investors
We found that a trillion-dollar IPO may change an index less than expected, but the active risk was real. We simulated the additions of SpaceX, OpenAI and Anthropic in the MSCI USA Index.
How Megacap IPOs in 2026 Could Reshape Global Benchmarks
Potential megacap IPOs in 2026 could reshape global benchmarks — increasing U.S. weight, shifting sectors toward software and aerospace and triggering billions in index flows.
1 We note that the impact will vary by index. In more concentrated benchmarks, weights could be meaningfully larger. Differences in index methodology, including free-float treatment and timing of inclusion, will also affect the stock’s weight in the index.
2 A long-noted strength of cross-sectional factor models; see Rosenberg, B. (1987). "Choosing a Multiple Factor Model." Investment Management Review, November/December, pp. 28–35.
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