08 — Portfolio Construction

Factor Models#

Decomposition✓ Mathematical
◆ The PatternDecompose returns into systematic factor exposures

CAPM uses a single factor (market beta). The Fama-French three-factor model adds size and value. Modern models include momentum, quality, and low-volatility.

ri = αi + β1F1 + β2F2 + … + εi
Factor tilts explain most of long-only active returns. Pure alpha — returns unexplained by any factor — is exceedingly rare.
// Factor decomposition — beta exposures
FactorPremium Source
Market (β)Equity risk premium
Size (SMB)Small-firm illiquidity
Value (HML)Distress / behavioral
MomentumUnder-reaction
Pattern bridge: Regression and betas are explored in The Toolkit — Regression.
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