22 April 2026

At The Money: Looking Beyond Market Cap Weighted Indexes

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7Insights

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Fundamental Economic Weighting

Weight companies by economic footprint instead of market price

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Insights & moments

The myth-busts, hot takes, explainers, and tools worth keeping.

Myth Buster· 1

Myth Buster01:53

Why Passive Indexes Have a Hyperactive Five Percent

Arnott argues that an index is not entirely passive when additions and deletions force it to trade. Most holdings merely move with the market, but the small turnover component behaves like an aggressive growth strategy that buys after major gains and may sell after severe losses.

Roughly 95% of an index can behave passively.
The turnover component makes consequential active trades.
Additions often follow strong relative performance.
Deletions can lock in large relative losses.

“What I've just described is the active side of indexing.”
Rob Arnott · 02:43

“The five percent looks like a hyper growth manager on crystal math.”
Rob Arnott · 03:20

#indexing#passive-investing#turnover#portfolio-risk

Hot Take· 1

Hot Take11:40

Growth Won Through Valuation Expansion, Not Faster Fundamentals

Arnott says growth indexes substantially outperformed value indexes even though their underlying sales, profits, book value, and dividends grew at roughly parallel rates. In his interpretation, much of the return gap came from investors paying increasingly high prices for growth fundamentals.

Growth indexes delivered large relative gains.
Growth became more expensive relative to fundamentals.
Value and growth fundamentals reportedly expanded at similar rates.
Price performance and business growth should be analyzed separately.

“The growth indexes have outperformed hugely, but they've outperformed by dint of becoming more and more expensive relative to fundamentals.”
Rob Arnott · 11:40

“the underlying fundamentals have grown in parallel.”
Rob Arnott · 12:25

#growth-stocks#value-stocks#valuation#fundamentals

Explainer· 2

Explainer03:43

How Index Reconstitution Creates a Crowded Trading Tax

Index funds seeking zero tracking error must transact at the effective closing price of an announced addition or deletion. Other traders can anticipate that compulsory demand, buy additions early, and later sell them to index funds at less favorable prices.

Index funds concentrate trades at predictable times.
Hedge funds can trade ahead of scheduled index changes.
The resulting drag is estimated at 15 basis points annually.
Low turnover can still produce a high cost per affected trade.

“I will pay whatever the price is at the close on the day that it's added to the index.”
Rob Arnott · 05:01

“It's a herd of elephants trying to go through a single revolving door.”
Rob Arnott · 06:36

#index-rebalancing#front-running#trading-costs#s-and-p-500

Explainer06:41

The Hidden Cost of Stocks Leaving and Rejoining the S&P 500

Arnott describes index flip-flops in which additions are later deleted or deleted stocks subsequently return. The index can miss the initial rise, participate in the collapse, and then miss much of the recovery before buying the company back.

About 28% of additions are later dropped within a decade.
Almost half of deletions return within a decade.
Added stocks had gained about 75 percentage points before entry on average.
Deleted-and-readded stocks outperformed dramatically before returning.

“If you gain seventy five and lose seventy, you aren't back where you started. You're down fifty, and it's worse than that because you didn't…”
Rob Arnott · 07:28

“So flip flops are very, very costly.”
Rob Arnott · 08:01

#index-changes#performance-chasing#s-and-p-500#behavioral-finance

Story· 1

Story14:44

Fundamental Indexing Endured a 13-Year Value Winter

Fundamental Index strategies launched in 2005, shortly before value peaked in 2007 and began a severe period of underperformance that lasted until 2020. Arnott uses the live history to illustrate the behavioral difficulty of maintaining a value-oriented allocation through a long unfavorable cycle.

Investable Fundamental Index strategies date to 2005.
Value peaked around 2007.
Severe underperformance persisted until summer 2020.
A value-tilted investor could become 38% poorer relative to a broad index at the trough.
Long factor cycles can test investor discipline for more than a decade.

“Value crested and it underperformed ferociously until summer of twenty twenty.”
Rob Arnott · 15:11

“You were thirty eight percent poorer than a simplest Russell or SMP index investor.”
Rob Arnott · 15:40

#value-cycle#underperformance#investor-discipline#live-track-record

Q&A· 1

Q&A12:30

Equal Weighting Works—But the Starting Stock Universe Matters

Equal weighting offers a legitimate alternative to market-cap weighting, adding small-cap and value exposure plus a systematic buy-low, sell-high rebalance. Its vulnerability is the selected universe: equal-weighting the S&P 500 still includes companies admitted after strong gains while excluding some companies made cheap by poor performance.

Every constituent receives the same allocation.
The method creates strong small-cap and value tilts.
Trimming winners and topping up losers can produce rebalancing alpha.
A market-cap-selected starting universe can retain valuation bias.
Long-run returns may resemble fundamental indexing but with greater variability.

“Equal Weighting is a perfectly legitimate way to create a portfolio.”
Rob Arnott · 12:48

“The only achilles heel that I think matters for equal weighting is equal weighting what stocks.”
Rob Arnott · 13:20

#equal-weighting#small-cap#value-investing#index-selection

Takeaway· 1

Takeaway16:20

The Claimed 20-Year Payoff From Fundamental Indexing

Arnott reports that live RAFFI indexes outperformed cap-weighted value indexes by slightly more than two percentage points annually over two decades. He says that compounded advantage left investors over 50% wealthier, with relative outperformance in approximately three out of every four years.

The comparison uses cap-weighted value indexes.
Reported compounded excess return exceeds 2% annually.
Compounding produced a claimed wealth advantage above 50% over 20 years.
Reported tracking error was about 2.5%.
The results come from live strategies rather than only a backtest.

“That means that you're over fifty percent richer than you were with a cap weighted value index after twenty years”
Rob Arnott · 16:44

“RAFFI has been winning at about three out of every four years, and this is live. This is not a back test.”
Rob Arnott · 17:17

#raffi#investment-performance#compounding#tracking-error