Event study
The three-day cumulative abnormal returns is estimated beginning on the
day prior to the end of class period date using event study methodology.
/ the three-day cumulative abnormal returns (CAR)
around the end of class period dates are calculated using a single-factor market model,
the CRSP equally-weighted market index and a 255-day estimation period that ends 45
days before the end of class period date, which is day 0.