https://www.jstor.org/stable/3088174 :
"Results show that layoff announcements trigger negative returns for both U.S. and Japanese firms. Specifically, layoff announcements of U.S. firms are associated with a negative 1.78 percent abnormal return ..."
https://onlinelibrary.wiley.com/doi/10.1111/1748-8583.12532 : "They find that investors do not react if a layoff announcement signals proactive management (e.g., cost cutting) but penalize the firm if the layoff indicates reactive management (e.g., decline in demand). The penalty is also positively associated with layoff size but unrelated to firm size. Further, investors have become less punitive over time, or if its stock is traded on an exchange in civil law (vs. common law) country. "