ex-dividend: change in the stock price when the stock goes ex-dividend

|Δp| * (1-T_CG) = D * (1-T_D)
|Δp| = D * (1-T_D)/(1-T_CG)


|Δp| : the change in the stock price when the stock goes ex-dividend (in absolute terms, since Δp < 0)
D: dividend declared per share
T_D : tax bracket for dividends
T_CG : tax bracket for capital gains

(e.g.)
D = 2.25
T_D = 15%
T_CG = 39.6%

|Δp| * (1 - T_CG) = D * (1 - T_D)
|Δp| = D * (1 - T_D) / (1 - T_CG)
= 2.25 * (1 - 15%) / (1 - 39.6%) = 3.1664... ≈ 3.17