Spread betting firm IG Index expects to post a strong rise in profits for the 12 months to March 31 after a good finish to the year.Adjusted pre-tax profits should come in at £125m, compared with £98m the previous year, on revenues that climb to £257m from £184m.The firm said year-on-year organic revenue growth was 18% in the final quarter, compared with 12% over the third quarter, despite lower market volatility.The reduction in volatility would have been expected to lead to less trading in indices and foreign exchange, IG said.The UK and Australian businesses, which saw revenues fall in the third quarter, performed better in the last quarter.