Spread-betting firm IG Group saw higher revenues in the three months to August 31, but said that volumes were subdued in the second half of that period and warned that future trends remain difficult to predict.Revenues were up to £79m from £68m in the same period the previous year. IG said that volumes were strong in the first half of the period but that the summer lull was amplified by low volumes in all the main asset classes in the second half.It reported higher revenues in Britain, Australia, mainland Europe, Singapore, Japan and the US. However at the beginning of August it saw a sharp fall in foreign exchange volumes in Japan as a restriction on leverage came into force. Japanese revenues totalled £6.5m, a 14% rise from the previous year.'It remains difficult to predict future trends in volatility or customer reaction to changing market and economic conditions,' the company said. 'Growth in the number of active customers and the continued development of the Group's offering leave the group well positioned for further growth.'