Focusing on Growth (Not Market Cap)

Episode Summary

Executive Summary: The episode is a wide-ranging interview with Rob Arnott about Research Affiliates’ Growth Index (RAFIG), a rules-based alternative to cap-weighted growth benchmarks. Arnott argues growth should be defined by real business expansion—sales, profits, and R&D—then weighted by the dollar contribution to economic growth, not market cap or valuation. He says the approach has delivered strong live and backtested outperformance, with higher volatility and sector-specific concentration but substantial capacity.

Main Topics: Why cap-weighted growth indexes are being questioned (Priority: 5/5): The conversation opens with concerns that cap-weighted benchmarks like the S&P 500 concentrate too much in a few mega-cap names, increasing valuation risk and market concentration. Growth should be defined by business expansion, not valuation (Priority: 5/5): Arnott rejects the common growth/value binary and argues that cheap vs. expensive and fast vs. slow growth are separate dimensions. He says growth indexing should identify companies actually growing rapidly. How RAFIG is constructed (Priority: 5/5): The index selects companies using growth in sales, profits, and R&D spending, averaging available growth measures. Companies are then weighted by the dollar magnitude of their contribution to economic growth. Performance and volatility tradeoff (Priority: 4/5): Arnott claims the index has outperformed Russell Growth meaningfully, but with somewhat higher volatility and occasional underperformance periods, which investors must accept. Concentration in mega-cap beneficiaries (Priority: 4/5): Despite not being cap-weighted, the index still includes very large growth contributors like Nvidia and Apple, while excluding names such as Apple, Amazon, and Microsoft in some periods if growth slows below the threshold. Capacity, turnover, and investability (Priority: 3/5): The discussion covers market capacity, turnover, and the idea that the strategy could eventually support a large ETF or mutual fund, though it is not yet investable. Research process and skepticism of data mining (Priority: 4/5): Arnott stresses that the strategy was built from a hypothesis and then tested, not mined from historical data, positioning it as an example of disciplined quantitative research.

Key Arguments: Cap-weighted growth indexes can over-concentrate in a few stocks, exposing investors to valuation and market-cap risk. Growth and value are not opposites; they are separate dimensions, so expensive stocks should not automatically be labeled growth stocks. A better growth index should select companies by actual growth rates in sales, profits, and R&D, not by valuation. Weighting by dollar contribution to economic growth avoids overemphasizing tiny firms that grow from a low base but contribute little in absolute terms. RAFIG has outperformed Russell Growth by about 4.5% annually over roughly 28-30 years in the research and has shown strong live performance. The strategy carries more volatility than cap-weighted benchmarks and requires investors to tolerate underperformance in some periods. Even with concentration in large growth leaders, the index has substantial capacity because turnover and targeted exposure limit scalability somewhat. The framework was designed by hypothesis first, not data mining, to reduce the risk of a fragile backtest that breaks in real markets.

Data Points: Outperformance vs. Russell Growth: 4.5% per annum - Arnott says RAFIG would have beaten Russell Growth by about 4.5% annually over nearly 30 years. Live outperformance since launch: 13 percentage points - The index is said to be ahead of Russell Growth since March 2023 on Bloomberg tracking. Performance range: plus or minus 7% - Arnott describes the long-run spread as 4.5% a year, with typical annual variation of about 7%. Winning years: about 7 out of 10 years - He says the strategy wins most years, but not all. Top constituents: NVIDIA and Apple - He names these as the two biggest holdings in RAFIG. Megacap exclusions: Apple, Amazon, Microsoft - He says two of the Magnificent Seven do not make the cut; Apple is explicitly named, and Amazon and Microsoft are mentioned as not growing fast enough currently. Relative weight of top names: a little over 10% each - Arnott says NVIDIA and Apple each represent slightly more than 10% of the index. Capacity estimate: 10% to 20% of the S&P 500 - He estimates RAFIG could have capacity equal to roughly a tenth to a fifth of S&P-based capacity. S&P index notional capacity reference: about $15 trillion - Used to estimate RAFIG’s approximate total capacity of $1.5T to $3T. Turnover estimate: 4x to 5x the S&P 500 - He suggests the strategy likely has materially higher turnover than the S&P. Historical live performance of RAFI Fundamental Index: 2% to 2.5% annual value add for 20 years - Arnott references the live record of the earlier fundamental index as evidence that their framework can work in practice.

Pivotal Quotes: "If it's expensive, it's expensive. It's much simpler. If it's growth, it's growth." — Rob Arnott: He is rejecting the idea that expensive stocks should automatically be categorized as growth. "Why don't we create an index that chooses growth stocks based on how fast they're growing and weights growth stocks based on how big their dollar contribution to the growth of the macroeconomy is?" — Rob Arnott: This is the core design principle behind the Research Affiliates Growth Index. "Scientific method means you start with a hypothesis and you only use the data to test the hypothesis." — Rob Arnott: He explains how the strategy avoids pure data mining and fragile backtests.

Implications: For investors, the episode suggests a path beyond cap-weighted growth toward fundamentals-based growth exposure with potential outperformance, but also more volatility and lower capacity than passive mega-cap benchmarks. It may influence future ETF design and indexing debates.