Tactical asset allocation (TAA) is the systematic adjustment of portfolio exposures based on forward-looking signals such as valuations, momentum, and macro regime indicators — as opposed to a fixed strategic benchmark.
Most investors treat a static strategic allocation as the neutral, unbiased option. It is not. A static 60/40 is constantly making a bet that the current expected return of equities relative to bonds justifies a fixed 60% weight — a bet that is almost certainly wrong most of the time. When equity earnings yield is 3% and bond yield is 5%, a static 60% equity allocation is a bet at negative edge. TAA is not about timing the market; it is about refusing to make the implicit bet at the wrong price.
CAPE's persistent bearish signal on US equities from 2010-2020 wasn't a flaw in the concept — it was a calibration error. The model was anchoring to a 150-year average CAPE of ~15 that included pre-1990 conditions: lower ROE, higher payout ratios, different sector composition. Post-1990, structural changes (technology-heavy economy, buybacks, higher capital-light ROE) permanently shifted the equilibrium CAPE higher. The model was right about the mechanism, wrong about the reference point.
TAA models with more parameters look more sophisticated and explain historical data better in-sample. They consistently underperform simpler models out-of-sample. The 1940s jeep analogy is apt: a system with fewer moving parts has fewer ways to fail in new conditions. Models that survive stress tests across many parameter perturbations are more likely to survive future regimes. The complexity that made the model look good in the backtest is the exact complexity that makes it fail live.