A pension committee tells you their $8B equity sleeve must be "indexed and cheap." That single sentence hides ten decisions: which index, which weighting scheme, which vehicle, which construction technique, and which tracking-error budget. CFA® Level III asks you to unpack each one.
Cap-weighting is the only portfolio every investor can hold simultaneously. If everyone held the cap-weighted market, the cross-section would clear. Any deviation (equal weight, value tilt, low-volatility tilt) is mathematically an active position that some other investor must take the opposite side of. That is the foundation of the "market portfolio is the neutral starting point" argument.
Cap-weighted indexing also delivers low turnover. When a stock's price rises, its weight rises automatically. The index does not need to trade to stay weighted. Equal-weighted, fundamental-weighted, and factor-weighted schemes all require periodic rebalancing that creates turnover, taxes, and transaction costs.
Factor-based strategies (sometimes called smart beta or strategic beta) tilt the portfolio toward documented return premia: value, size, momentum, quality, low volatility, dividend yield.
Common mistakes
- Calling factor strategies "passive." They are rules-based but they are active relative to the cap-weighted market. A pension that books a value-weighted ETF in the passive bucket misclassifies 2-6% expected tracking error as zero.
- Ignoring withholding tax drag on foreign benchmarks. Comparing a US-domiciled World index fund to the gross MSCI World index produces a structural shortfall of 15-30 bp annually. Use the "net" index or a tax-aware benchmark.
- Treating securities lending revenue as alpha. It offsets fees and lowers tracking error but it is not skill. The exam treats lending revenue as a passive return source, not as manager value-add.
Bottom line
- Cap-weighted indexing is the only macro-consistent neutral portfolio; every alternative weighting (equal, fundamental, factor) is an active bet against it.
- Factor-based strategies are rules-based but active relative to the market; expect 2-6% tracking error, so booking them as passive misclassifies that risk as zero.
- Three construction techniques: full replication for liquid large-cap benchmarks, stratified sampling for broad or illiquid indexes, optimization when constraints or factor matching dominate.
- Tracking error sources: fees, cash drag, sampling, transaction costs, corporate-action timing, withholding taxes, index reconstitution.
Exam shortcut
When the vignette names a benchmark, count constituents. Under 1,000 liquid names with no client constraints points to full replication; broad or illiquid benchmarks point to stratified sampling; named constraints (ESG screens, tax-loss harvesting, factor overlay) point to optimization. For vehicle selection, match the binding constraint to the vehicle. Intraday liquidity needed: ETF. Lot-level tax control: SMA. Temporary exposure during a manager search: futures. Restricted-market access: swap.
The full lesson (about 3,578 words, 24 min read) adds 2 worked examples, all 6 common mistakes, a self-check, free in the app.
Learning objectives
- passive equity investing
- index construction
- portfolio construction
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