COVID-19 and the Health Industry: A Test of Market Efficiency
Bibliographic record
Abstract
The World Health Organization declared the COVID-19 coronavirus outbreak as a global pandemic on March 11, 2020. How does the market react to a global pandemic announcement? How efficient is the market? The purpose of this study is to test for semi-strong form market efficiency. Will the healthcare industry show excess gains? A link between the market and pandemics can be inferred but has not been heavily studied. In the efficient market hypothesis, Fama (1970) proposes that in semi-strong form market efficiency, all public information is factored into the market and no investor can achieve a risk-adjusted, above normal return. To study this relationship, S&P 500 data on 10 healthcare firms was collected for several days surrounding the announcement and standard event study methodology from finance literature was used. Evidence here supports the expected positive signal associated with the sample firms and pandemic announcement. Likewise, the results support the semi-strong form efficient market hypothesis and suggests the possibility of trading on this information up to 24 days before the announcement.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.007 | 0.035 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".