Consider a dividend paying stock $S$ and suppose that its value just before a dividend payment of $D >0$ at time $t$ is denoted by $S(t−)$. The price after the payment should be $S(t)=S(t-)-D$?
How can I justify that. Is there an arbitrage argument?
Consider a dividend paying stock $S$ and suppose that its value just before a dividend payment of $D >0$ at time $t$ is denoted by $S(t−)$. The price after the payment should be $S(t)=S(t-)-D$?
How can I justify that. Is there an arbitrage argument?
If a stock price is the discounted value of future income, then immediately before the dividend, the future income is the amount $S(t-)$, and immediately after the dividend, the future income is the amount $S(t) = S(t-)-D$. It's lessened by $D$ because that's no longer part of the stream of future income. There's nothing more to it than that.
Not necessarily, because of tax considerations. Depending on the jurisdiction, capital gains may be taxed at a different rate than dividends. Depending on these rates, selling a stock before the dividend at $S(t-)$ may be a better or a worse deal than getting the dividend $D$ and selling at $S(t-)-D$. If enough investors prefer one to the other, it will affect the stock prices.