About the Index

Which companies truly drive the U.S. stock market?

The three most-watched U.S. indexes — the S&P 500, Nasdaq-100, and Dow Jones Industrial Average — are each constructed differently. Yet a handful of companies appear in all three, and their movements disproportionately shape headline market performance. The Leading Horsemen Index (LHI) is a quantitative attempt to isolate exactly which companies exert the most influence on the U.S. equity market.

34.6%

Top 10 concentration

Ten companies account for over a third of combined index weight.

52.3%

Top 25 concentration

The Leading Horsemen represent more than half of all market-cap-weighted exposure.

3×

Overlap multiplier

Mega-cap constituents are counted across SPY, QQQ, and DIA, amplifying their market impact.

Motivation

Why build a new index?

Traditional benchmarks track distinct segments of the market. But investors, analysts, and journalists routinely speak of "the market" as a single entity — usually meaning some blend of the three flagship indexes. No public metric measures this composite influence.

LHI fills that gap. By normalizing constituent weights across all three indexes, it produces a single Market Influence Score for every U.S. large-cap. The score answers a clean question: if we treat the headline market as one thing, which companies actually move it?

Research

Isolates the true influencers behind headline market moves.

Unification

Blends three distinct index methodologies into one composite.

Normalization

Reweights across differing constituent counts and rules.

Signal

Tracks influence over time — not just weight, but persistence.

Speed

Refreshed monthly, aligned to end-of-month rebalancing cycles.

Transparency

Fully reproducible methodology and open-sourced calculations.

See the methodology in detail

Seven-step workflow, from raw holdings to Market Influence Score.

View Methodology →