Research note: This material is for educational and strategy-design purposes. It is not investment advice or a promise of future returns.
Executive summary
Post-earnings announcement drift, or PEAD, buys stocks after strong positive earnings surprises and avoids or shorts those with negative surprises, on the premise that prices continue to drift in the surprise direction after the announcement. Bernard and Thomas established this as one of the classic underreaction anomalies.
In India, PEAD is highly operational because quarterly results are concentrated disclosures with exact dates, regular exchange filing flows and measurable gaps. The challenge is not theory; it is clean surprise measurement and event-time execution.
Description
The strategy needs two things: an unexpected earnings measure and a post-event holding rule. The unexpected earnings measure can be formed from analyst consensus surprise, seasonal random-walk earnings surprise or management-guidance shock. The holding rule is usually 20–60 trading days after the announcement, but may be shorter in large-cap India if diffusion is faster.
PEAD is not the same as revision momentum, although the two reinforce one another. PEAD keys off the announcement surprise itself; revision strategies key off the path of expectations. In practice, many PMs blend the two because the joint signal is cleaner than either signal alone.
Key attribute table
The range below is a practical inference from PEAD literature and institutional event-implementation experience.
| Time horizon | Turnover | Typical Sharpe or return expectation | Data needs | Complexity | |---|---|---|---|---| | Event-driven short to medium term | High | Sharpe roughly 0.5–1.0; annualised return target roughly 8–16% gross | Results dates, surprise data, event-time prices | High |
Details
Universe: liquid NSE large-mid caps with reliable event timestamps. Signal: standardised earnings surprise, preferably (reported EPS − consensus EPS) / price or a standard deviation scale. Enter the trade at next-session open if surprise is positive and above threshold; exit after 20 to 40 trading days or earlier if a trailing-stop or reversal rule triggers. Use symmetric negative-surprise avoidance or shorting only if the mandate supports it. NSE corporate filings and financial-result announcements provide the official event calendar backbone.
Risk controls: cap exposure to event clusters within the same sector, impose no-trade rules when results are announced during illiquid auction windows or immediately before holidays, and watch for guidance reversals during conference calls. Position sizing should be smaller than for slow factors because event dispersion is high. Use a same-day maximum gap filter to avoid chasing extreme one-day overreactions.
Backtests must align precisely to public release times and next-implementable trade times. Edge cases include restated results, split-adjusted EPS confusion, result leaks and simultaneous corporate actions. If the desk cannot trade near the event cleanly, the strategy becomes a slower earnings-momentum sleeve rather than pure PEAD.
flowchart TD
A[Result announced to exchange] --> B[Measure earnings surprise]
B --> C{Surprise above threshold?}
C -->|Yes| D[Enter next-session long]
C -->|No, strongly negative| E[Avoid or short if allowed]
D --> F[Hold twenty to forty trading days]
E --> F
F --> G[Exit on time, stop, or reversal]
Implementation guide
- Pull exact result-announcement dates from official exchange filings.
- Calculate standardised surprises using a timestamped expectation baseline.
- Enter only after the announcement is public and tradable.
- Hold for a defined event window.
- Cap event and sector concentration.
- Review decay half-life by market-cap bucket.
India-specific example
Suppose TCS reports quarterly EPS of ₹35 against a pre-event consensus of ₹33.5. The surprise is +₹1.5, or +4.5% relative to consensus. If the model threshold is +3%, TCS becomes a long candidate at the next feasible session. If another name, say CIPLA, posts a mild surprise of +0.7%, it may fail the threshold and generate no trade. That framing is consistent with PEAD logic: only sufficiently large surprises should justify event risk and turnover.
A ₹5 crore event sleeve may size a single PEAD trade at 4–5% NAV, then hold for 20 trading days unless a stop or competing information event occurs. Because Indian stocks often gap at the open after results, assume adverse slippage around entry and avoid backtests that fill at the previous close. Trades occur in normal NSE hours, and shorting requires either derivatives or a borrow-enabled infrastructure.