M&A Event Study
Pre- and post-acquisition return dynamics across HIP groups
High-HIP firms gain +22% cumulative abnormal return leading up to the deal, but give back most gains afterward.
Low-HIP firms start slow but end up ahead by month 6 post-event - a pattern mirroring the annual return reversal.
The crossover at t+6 echoes the same structural reversal seen in the broader annual returns data.
Peak High HIP CAR
+0.0%
Crossover Point
t+6
months post-event
Post-Event Reversal
0.0%
High HIP decline
H-L Spread at t+12
0.0%
High minus Low
CAR trajectory from t-12 to t+12 months
t-12 to t-1
Market anticipates the deal. High-HIP firms build momentum as investors expect ESG quality to drive acquisition success.
t = 0
M&A deal is announced. Maximum separation between HIP groups - High HIP peaks at +22% CAR.
t+1 to t+3
Initial market reaction. High-HIP advantage begins to erode as integration challenges emerge.
t+3 to t+6
Groups converge. The ESG premium disappears as real integration performance matters more than ratings.
t+6 to t+12
Complete reversal. Low-HIP firms surpass High-HIP firms, suggesting initial premium was overreaction.
| Period | High HIP | Medium HIP | Low HIP | Spread (H-L) |
|---|---|---|---|---|
| t-12 | 2.0% | 1.0% | -1.0% | +3.0% |
| t-9 | 5.0% | 3.0% | 1.0% | +4.0% |
| t-6 | 8.0% | 5.0% | 2.0% | +6.0% |
| t-3 | 12.0% | 8.0% | 4.0% | +8.0% |
| t-1 | 15.0% | 10.0% | 5.0% | +10.0% |
| Event | 22.0% | 15.0% | 8.0% | +14.0% |
| t+1 | 18.0% | 14.0% | 9.0% | +9.0% |
| t+3 | 14.0% | 12.0% | 10.0% | +4.0% |
| t+6 | 10.0% | 11.0% | 12.0% | -2.0% |
| t+9 | 6.0% | 9.0% | 13.0% | -7.0% |
| t+12 | 3.0% | 7.0% | 14.0% | -11.0% |
- Event window: [-12, +12] months around announcement
- Estimation window: [-252, -13] trading days
- Benchmark: CSI 300 Index
Markets may initially overvalue the ESG quality of acquiring firms. The pre-event run-up and post-event reversal is consistent with investor overreaction, where enthusiasm about ESG-aligned deals fades as actual integration performance becomes visible.