A Major Reshuffle: How MSCI’s New Rules Will Transform the World’s Largest ETF

A landmark shift in methodology is set to reconfigure the MSCI World Index in May 2026, marking its most significant overhaul in years. The changes will recalibrate the influence of its largest holdings, directly impacting the globe’s most popular exchange-traded fund tracking this benchmark.

The Core of the Change: A New Free-Float Framework

The upcoming revision centers on the introduction of a refined free-float calculation system. Index provider MSCI will implement three distinct categories for classifying a company’s freely tradable shares: “high” (above 25%), “low” (between 5% and 25%), and “very low” (under 5%). Each tier will be subject to more precise rounding rules. The objective is to achieve a more accurate representation of the actual market liquidity of a firm’s equity.

This technical adjustment is expected to trigger substantially higher portfolio turnover compared to a standard quarterly rebalancing. Notably, the weightings of individual mega-cap stocks—including current top holdings like Nvidia (5.47%), Apple (4.53%), and Microsoft (3.58%)—are likely to see noticeable adjustments.

A Quiet Prelude Before the Storm

Anticipating this major change, MSCI deliberately executed a conservative rebalancing in March. The Q1 review saw only 18 additions against 27 deletions, with the U.S. market alone witnessing 8 new entrants and 15 removals. This restrained approach was designed to avoid unnecessary turnover ahead of the May methodology transition.

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A subtle but notable shift occurred during this review: the index’s exposure to the United States was slightly reduced for the first time in several years. Among the companies added were AST SpaceMobile and Coherent Corp., both with ties to the expanding artificial intelligence infrastructure sector.

Crypto Classification Decision Postponed

In a related development, MSCI has delayed a closely watched decision regarding companies with significant cryptocurrency holdings. Firms classified as “Digital Asset Treasury Companies” will, for now, remain part of the index. MSCI stated that distinguishing between investment firms and companies holding digital assets as part of their core operations requires further research and market consultation. Concrete actions on this front have been postponed indefinitely.

For affected index constituents such as Strategy Inc., this reprieve means the threat of immediate passive selling pressure has been temporarily lifted.

Implications for the Leading ETF

The iShares Core MSCI World UCITS ETF (Acc), which manages approximately €112 billion in assets, is the largest ETF tracking the MSCI World. The full effect of the methodological reform will become apparent during the May review, when the new calculation rules are applied to the weightings of the world’s largest corporations. The fund’s composition will subsequently be adjusted to mirror these changes, potentially altering the exposure for millions of investors who use this fund as a core global equity holding.