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Market surveillance notice
n=282as of 2026-07-09
Surveillance notices such as attention-trading disclosures.
| Window | Benchmark | n | Mean abnormal return | Median | q value | Significant |
|---|---|---|---|---|---|---|
| 5 trading days after | CAR | 251 | -2.57% | -3.82% | 0.008 | Yes |
Method: the filing's public-availability date is day 0, with a conservative entry on the following trading day. CAR (cumulative abnormal return) is estimated with a market model and calibrated by a placebo test that keeps the event dates but draws random same-day tickers. BHAR (buy-and-hold abnormal return) is measured against size- and liquidity-matched control stocks. All tests carry a multiple-testing correction (BH-FDR). Where the two benchmarks disagree, both are shown as they are — we do not pick the flattering one.
Frequently asked questions
How do Taiwan share prices behave after a market surveillance notice goes out?
Across n=282 historical events measured by this site's event study engine, mean abnormal return -2.57% over the 5 trading days after the event (CAR benchmark). Both CAR and BHAR benchmarks are presented, flagged where they disagree. This is not investment advice.
How large is the sample when a market surveillance notice goes out?
282 events, as of 2026-07-09, of which 4 statistical cells clear the significance threshold.
Other event categories
The above is a statistical view of historical events (base rates). It is not investment advice and not a trading signal; a historical distribution does not guarantee the future repeats it. Source: This site's event study engine (computed in-house from official public-source event data; editorial copyright)