Sentiment Proxies Have Information. They Are Not a Timing System

Sentiment moves prices away from any reasonable estimate of value for longer than most people can stay solvent. De Long, Shleifer, Summers and Waldmann formalised the noise-trader risk: rational capital faces the chance that the mispricing widens before it corrects, and the agents deploying that capital can be fired or redeemed before the correction arrives. Julian Robertson closed Tiger in March 2000, the month of the Nasdaq peak, after being right about valuations and wrong about client patience. Being early and being wrong produced the same P&L.

That is the practical boundary. Proxies can show you when positioning and narrative are stretched. They cannot tell you the day the stretch ends.

What the common proxies actually capture

The VIX measures 30-day implied volatility from S&P 500 options. Readings above 40 have historically coincided with attractive subsequent entry points. Readings below 12 have coincided with complacency. High VIX can also persist for months in genuine crises. Being early is expensive.

The AAII survey polls individual investors on their six-month outlook. Extreme bearish readings have preceded above-average forward returns more often than moderate readings. The sample is small and retail-biased. It is a contrary indicator at the tails, not a weekly signal.

Put/call ratios reflect hedging and speculation. Elevated put buying can signal fear. It can also reflect institutional hedging that has nothing to do with directional bets. The signal is noisier than the headline suggests.

FINRA margin debt has peaked ahead of major bear markets over the last forty years. Large two-month increases, such as the $119 billion rise in late 2020, have marked periods of elevated speculative leverage. The lag between the peak and the subsequent decline varies.

Jay Ritter’s IPO database shows average first-day returns. Readings of 65–71 percent in 1999–2000 were historically anomalous and coincided with the bubble peak. The long-run average is closer to 17–19 percent. Extreme pops are a sentiment thermometer, not a sell date.

Baker and Wurgler’s composite index (turnover, IPO volume and first-day returns, closed-end fund discounts, equity issuance share, dividend premium) predicts cross-sectional returns. High sentiment forecasts subsequent underperformance of speculative stocks. Aggregate market timing power is weaker and sample-dependent.

Magazine covers and mass advertising of speculative assets have a long anecdotal record as exhaustion signals. Time’s June 2005 housing cover preceded the peak in home-price growth by weeks to months. The February 2022 Super Bowl crypto ads arrived after Bitcoin had already peaked and before the subsequent collapse. The mechanism is simple: by the time a story reaches a general-news cover or a Super Bowl ad, the pool of new buyers is largely exhausted. The timing is still not precise.

How to use them without fooling yourself

Treat aligned extremes across several proxies as a regime flag, not a trade. High sentiment plus extreme IPO pops plus elevated margin debt raises the probability that speculative names will underperform. It does not tell you to short the index tomorrow. Low sentiment plus extreme VIX plus record fund outflows raises the probability of attractive forward returns. It does not remove the possibility that prices go lower first.

The cross-sectional result is more reliable than the aggregate timing result. Speculative, hard-to-arbitrage stocks are most sensitive to sentiment waves. A value process can use extreme fear as a place to look for discounts. A momentum process needs to know that the same names that led on the way up usually lead on the way down when sentiment reverses. A passive process owns the full cycle and needs a plan for the drawdown the reversal produces.

Market structure has changed. Passive flows, ETF arbitrage and retail options activity alter how sentiment transmits to prices. Any fixed weighting or threshold needs re-validation. There is no proxy that dominates a disciplined multi-factor process across all regimes.

What to do with this

Pick two or three proxies you can actually check without daily obsession. Write the extreme levels that would constitute a regime flag for your process. When those levels are hit, review position sizes and invalidation rules. Do not add a new timing overlay on top of an existing method. The overlay usually costs more than it saves.