NEW DELHI; With oil prices so low, India's economic growth should have been back at over 9 per cent, Former Chief Economist at World Bank Kaushik Basu said today, expressing disappointment at the 6.3 per cent GDP expansion in the September quarter."India's growth rate is now 6.3 per cent. It had reached a rate of 9.5 per cent from 2005-2008," Basu, who was also Chief Economic Adviser during the UPA government , said in a tweet."Now with oil prices so low, the growth should have been back at over 9 per cent. This massive slowdown needs to be properly diagnosed," he added.The GDP growth in the second quarter of 2017-18 was 6.3 per cent, compared to 5.7 per cent in the April-June period -- the lowest growth rate since the Modi government took office.It was 7.5 per cent in the September quarter of last fiscal.