Investor Psychology and Security Market Under- and Overreactions

Source: Daniel, K., Hirshleifer, D. & Subrahmanyam, A. (1998). Journal of Finance 53(6),

1839–1885.

TL;DR

A behavioral asset-pricing model built on two psychological biases — overconfidence (investors

overestimate the precision of their private information) and biased self-attribution (they credit

confirming outcomes to skill, dismiss disconfirming ones as bad luck). Together these generate

short-horizon momentum / continuing overreaction, long-horizon reversal, excess volatility, and

public-event-based return predictability — a unified account of the major return anomalies.

Can a single, well-grounded model of investor psychology jointly explain the pervasive return anomalies

that challenge market efficiency: (1) public-event return predictability, (2) short-term momentum,

(3) long-term reversal, (4) excess volatility, and (5) post-earnings-announcement drift? The authors

argue these patterns are too strong and regular to be chance, and that rational-risk-premium

explanations would require implausibly extreme variation in marginal utility.

Risk-neutral, overconfident informed investors receive a noisy private signal and a public

signal; overconfidence means they overweight the precision of the private signal.

This overweighting pushes price past fundamental value on private information → overreaction, while

the public signal is underweighted → underreaction to public news.

Biased self-attribution: when a later public signal confirms the prior private signal, the investor's

confidence rises further, so overreaction continues rather than correcting immediately.

Eventually accumulating public information draws price back to fundamentals → correction/reversal.

Overconfidence alone ⇒ negative long-lag autocorrelations (long-term reversal), excess volatility,

and event-based predictability when managerial actions correlate with mispricing.

Self-attribution added ⇒ positive short-lag autocorrelations (momentum) and short-run earnings

drift, but negative correlation between future returns and long-term past stock/accounting

performance.

Public events that occur in response to mispricing (e.g., issuance, repurchase) predict subsequent

same-sign drift then opposite-sign long-run performance.

Matches the documented joint pattern of underreaction at short horizons and overreaction at long

horizons; sits alongside Barberis-Shleifer-Vishny (1998) and Hong-Stein (1999) as a foundational

behavioral explanation of momentum, reversal, and post-event drift that the efficient-markets view

must contend with. Several of its implications were untested at publication.

The biases are assumed (and calibrated), not derived from primitives; it rationalizes known anomalies

more than it predicts new ones.

A stylized model that abstracts from arbitrage forces and investor heterogeneity; overconfident traders

are not competed away.

Daniel, K., Hirshleifer, D. & Subrahmanyam, A. (1998) — Investor Psychology and Security Market Under- and Overreactions — Journal of Finance

Barberis, N., Shleifer, A. & Vishny, R. (1998) — A Model of Investor Sentiment — Journal of Financial Economics

Hong, H. & Stein, J. (1999) — A Unified Theory of Underreaction, Momentum Trading and Overreaction — Journal of Finance

Provenance: verified/generated from the paper's full text.