Equity Strategy · 8 min read · 2026-05-05
The 9-signal post-earnings drift playbook.
PEAD has been documented for fifty years and survives in plain sight because most retail and many institutions still trade earnings as a single-day event.
A 50-year-old anomaly the market still has not arbitraged away.
Stocks that beat earnings continue to drift up — and stocks that miss continue to drift down — for 30 to 60 trading days post-announcement. The effect, first documented by Ball and Brown in 1968, has shrunk but not vanished. The nine-signal screen separates the drifts that compound from the bounces that mean-revert.
The nine indicators
The nine indicators of a tradable earnings drift.
PEAD does not trade as a blanket strategy. It works in the subset where surprise size, fundamental confirmation, and information-diffusion friction line up.
Standardized unexpected earnings (SUE) above 2.0
Threshold: SUE > 2.0
SUE normalizes the surprise by the standard deviation of recent surprises. Above 2.0 means the surprise is two standard deviations above expectations and statistically meaningful.
Revenue surprise in the same direction as EPS
Pattern: both beat or both miss
Top-line surprises confirm the bottom-line surprise as fundamental rather than tax or one-off driven. Mixed surprises (EPS beat with revenue miss) drift more weakly.
Forward guidance moved in the surprise direction
Pattern: guide raised on beat
When management raises guidance with a beat, the drift extends. When they 'beat and reset' guidance lower, the drift is short-circuited within five trading days.
Analyst revisions lag the announcement by 5+ days
Lag: > 5 trading days
Information diffusion through the sell-side is slow. The first wave of revisions hits within 48 hours; the second and third waves continue for two to three weeks. The drift compounds while revisions are still arriving.
Earnings call sentiment matches the print direction
Tool: NLP polarity score
A beat with a cautious call drifts less than a beat with a confident call. Quantitative parsing of the call transcript adds 10–15% to the drift-prediction R².
Options put-call skew flattening on a beat
Signal: skew flattening
Skew flattening on a beat is the option market confirming the move. Persistent put-side richness despite a beat is a fade signal.
Insider activity confirming direction
Form 4 within 30 days
Cluster insider buying in the 30 days post-beat (or selling post-miss) confirms the direction. Insider trades within the legal window after earnings carry information.
Volume profile concentrated on up days (post-beat) or down days (post-miss)
Up/down volume ratio > 1.4 (post-beat)
Volume concentration on the side of the surprise is institutional accumulation. Volume on the opposite side is liquidity unwind.
No competing macro event inside the drift window
FOMC, CPI, earnings macro overlap
Drift compounds in clean information environments. When a major macro event lands inside the drift window, the signal is overwhelmed.
What PEAD is, and why it persists
Post-earnings announcement drift is the tendency of stocks to continue moving in the direction of an earnings surprise for 30 to 60 trading days after the announcement. The phenomenon has been documented continuously since Ball and Brown (1968) and is one of the most studied anomalies in finance. It has not been arbitraged away.
The persistence has a behavioral explanation. Information from earnings calls diffuses unevenly: institutional analysts revise their estimates over a period of one to three weeks; retail investors react over a longer tail; quantitative model owners rebalance on a discretionary schedule. The price moves in steps as each wave of buyers (or sellers) arrives. By the time the information is fully reflected, 30 to 60 days have elapsed.
Why blanket PEAD trades have stopped working
Two decades ago, a simple long-the-top-decile-of-surprise / short-the-bottom-decile portfolio earned 60–80 basis points per month. That alpha has been compressed to 15–25 basis points across the last decade as quantitative strategies have crowded in. The blanket trade still has a positive expected value, but it is no longer interesting on a Sharpe-adjusted basis.
What still works is the conditional trade. PEAD persists in the subset of names where the information is genuinely fundamental, the diffusion friction is high, and competing factors do not overwhelm the surprise signal. The nine-signal screen identifies that subset.
SUE — the right way to measure surprise
Standardized unexpected earnings normalizes the surprise by the standard deviation of recent surprises for the same company. A 5% EPS beat for a stable consumer name is a meaningful surprise; a 5% beat for a highly volatile tech name is noise. SUE adjusts for this. A SUE above 2.0 means the current surprise is more than two standard deviations above the recent surprise distribution and is the threshold above which drift effects become statistically reliable.
The revenue confirmation
An EPS beat that comes from cost-cutting, a lower tax rate, or a one-off gain does not drift. An EPS beat accompanied by a top-line beat is a genuine demand surprise and drifts. The screen requires both. Mixed surprises, where EPS beats but revenue misses, are the most common false positives in PEAD trading and a regular source of frustration for naive strategies.
Why guidance is the most important confirmation
Management's forward guidance is the most direct private-information signal about the business. A beat accompanied by raised guidance is the cleanest possible PEAD setup; the drift typically extends two to three weeks longer than a beat with maintained guidance and four to six weeks longer than a beat with reset-lower guidance. Conversely, a miss with raised guidance often produces a counter-drift — the stock falls into the print and recovers as the guidance reality lands.
The signal is asymmetric in execution. Guidance language is contained in the press release and amplified on the call. NLP scoring of the language captures the nuance better than the raw beat-or-miss dichotomy.
Trading the drift — practical structure
The historical edge comes from long entries 1–3 trading days after the announcement and exits 30–45 trading days later. Entering on day zero captures the announcement-day move (which is not part of PEAD); entering after day five typically misses the strongest part of the drift. The middle of the first week is the optimal entry point.
Position sizing matters. A 9-of-9 alignment is rare — perhaps three to seven names per quarter across the U.S. large-cap universe. Each position should be sized 1–3% of the portfolio. The strategy is additive, not core; it is layered onto a baseline equity allocation as a satellite.
What to avoid
Do not trade PEAD around macro events. CPI prints, FOMC announcements, payroll reports, and major geopolitical events flatten or invert the drift signal by introducing a competing factor. The screen should exclude any window within five trading days of a top-tier macro event.
Do not trade PEAD in micro-caps. Information diffusion in small-caps is fast and the drift is short. The strategy works best in the $5B–$200B market cap range, where institutional ownership is high and the diffusion friction is greatest.
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Common questions
Questions.
Is PEAD still alive in 2026?
Yes, but compressed. The blanket portfolio earns 15–25 bps per month; the conditional portfolio (nine-signal screen) still earns 50–70 bps per month in the historical sample, before transaction costs.
Does PEAD work outside U.S. equities?
Versions of PEAD have been documented in most major equity markets, but the magnitude varies. European PEAD is roughly two-thirds the magnitude of U.S.; Japanese PEAD is roughly half. The information-diffusion mechanism is universal; the analyst coverage and dissemination cadence varies.
Can I trade PEAD with options?
Yes. Long calls 30–45 days to expiration, struck at-the-money, capture the drift with defined risk. The cost is theta and skew; the benefit is asymmetric exposure with a cap on the loss.
How does PEAD interact with momentum factors?
PEAD is a short-horizon component of momentum. Pure momentum factors capture 6–12 month price persistence; PEAD captures the 1–2 month earnings-driven subset. They are correlated but not identical.
What's the holding period?
Historical optimum is 30–45 trading days. Shorter holding periods miss the back-half of the drift; longer holding periods accumulate noise from the next quarterly cycle.
Is PEAD risk-on or risk-off?
Risk-on. The drift compounds in trending markets and is dampened in choppy or risk-off regimes. The macro overlay (signal #9) excludes the worst regimes from execution.
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