"We are re-launching Sensex and Bankex derivatives with lower lot sizes and a new expiry cycle of Friday from May 15. The launch of Sensex 30 and Bankex derivatives will provide investors an opportunity to trade these popular and well-tracked indices,'' he said. The Sensex and Nifty have a 99.92 per cent correlation, while Bankex and Nifty Bank have a 99.97 per cent correlation, according to historical trading data over the past 11 years.