Webinar: Mitigating Market Concentration Risk With RAFI Indices

In a recent webcast hosted by TMX VettaFi’s Head of Research Todd Rosenbluth, Ari Polychronopoulos, TMX VettaFi’s head of RAFI Indices joined Brent Leadbetter, TMX VettaFi’s head of RAFI Distribution, to address the growing market concentration risk within broad equity benchmarks. Forty-three percent of webinar attendees noted that market concentration is the greatest risk to investor portfolios in the current market environment. With that, Polychronopoulos and Leadbetter outlined how nonmarket-cap-weighted strategies can help restore portfolio diversification.

• As broad equity benchmarks become increasingly dominated by a handful of mega-cap technology stocks, nonprice-weighted strategies offer an effective structural tool for restoring portfolio diversification.
• By selecting and weighting companies according to real economic metrics like sales, cash flow, dividends, and book value, the RAFI methodology enforces a systematic “buy-low, sell-high” rebalancing process that mitigates valuation risk.
• RAFI multifactor and growth strategies enable investors to target operational expansion while maintaining broad market breadth.

See More: Why RAFI Serves as an Effective Core & Stronger Value Allocation

Ari opened by noting that market concentration has reached historic levels. The Magnificent Seven mega-cap technology stocks represent roughly 35% of the S&P 500. That cohort carries a combined market cap exceeding $20 trillion. To understand the scale of this market concentration, that figure is larger than every national stock market outside the U.S. combined. To put this in further perspective, Ari posed a question to investors: “Would you rather, as an investor, own basically these seven stocks, or every single publicly available equity in Europe and the United Kingdom, whose profits really dwarf these seven companies alone?”

Traditional market-cap-weighted indices automatically allocate more capital to companies as their share prices rise. In effect, this creates a momentum-driven loop that exposes investors to extreme valuation risks. Pointing to historical cycles like the 2000 dot-com unwinding, Ari noted that while the cap-weighted S&P 500 fell 22% over two years, the average constituent stock actually rose 25%. This ultimately demonstrates how top-heavy concentration can drag down broader index returns when market multiples mean-revert.

To break the link between market price and index weight, the RAFI Fundamental Indexing methodology selects and weights constituents by economic scale using four fundamental measures: adjusted sales, cash flow, dividends plus buybacks, and book value. Leadbetter explained that while economic sector weights naturally evolve slowly, price-weighted market cap indices experience volatile sector spikes like technology in 2000.

By anchoring portfolio weights to real economic metrics, RAFI operationalizes a systematic, contrarian “buy-low, sell-high” rebalancing process. Over time, this dynamic generates a structural value tilt that deepens when market valuation spreads widen, which have historically delivered consistent excess returns over long investment horizons.

“When you’re selecting and weighting by fundamentals, you are breaking that link between price and weight in your index construction process,” Ari explained.

“You’re systematically selling what’s done well and buying what’s done poorly,” he added. “And that’s really the key to understanding fundamental weighting.”

When it comes to factor investing, Ari emphasized a multifactor approach. This involves blending complementary, low-correlation factors like value, low volatility, quality, momentum, and size. In doing so, this offers investors another effective strategy to mitigate concentration risk. One of the funds highlighted was the PIMCO RAFI Dynamic Multi-Factor US Equity ETF (MFUS B+), which dynamically weights factor sleeves based on valuation and momentum.

Additionally, Leadbetter introduced RAFI’s research into fundamental growth indexation. In so doing, he noted that traditional growth indices simply default to expensive stocks. Alternatively, true growth, according to RAFI Indices, decouples itself from price.

“Actual growth managers look for growth,” Leadbetter explained. “They don’t look for expensive firms.”

“Instead of taking a traditional approach, what we’ve done is decided to select and weight companies by fundamental measures of growth,” he added. “This includes metrics like sales growth, profitability growth, R&D growth.”

Ultimately, fundamental strategies provide investors with transparent, rules-based indices designed to manage valuation risk and achieve long-term capital appreciation through shifting market environments.

To watch the full webinar, click here.

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VettaFi LLC (“VettaFi”) is the index provider for MFUS, for which it receives an index licensing fee. However, MFUS is not issued, sponsored, endorsed, or sold by VettaFi, and VettaFi has no obligation or liability in connection with the issuance, administration, marketing, or trading of MFUS.