Hi, I want to know what happens to bank nifty index value and the futures price when a stock in the index does ex dividend? Do they recalculate the index value according to the new lower ex dividend price?
After the announcement of dividend, the stock (not futures) should move up because people buy the stock to earn the dividend. The futures don't move since you don't get dividend for holding futures. Ex- dividend, the stock falls (theoretically equal to the dividend) and futures remain where they are.
So, stock goes up and then down and futures remain where they are (as long as announcement of dividend is the only factor affecting the price movement of course).
Yes, Bank Nifty index will be recalculated based on the new price of the constituent stock. Bank nifty futures remain unaffected.
Edit:
Or more correctly, as soon as the dividend is announced, there is a small arbitrage opportunity and stock goes up and the futures down (you won't be able to take advantage because you don't know when the dividend is announced). And when the stock goes ex- dividend, the futures won't move (because it's already discounted the ex-dividend price) but stock comes down.