India is set to overhaul how it calculates real GDP growth under a revised national accounts series due to launch this week, the country's top statistical official said, adopting more granular price deflation to address concerns raised by economists. “We will now use about 500-600 items from the new CPI and the old WPI series, compared with about 180 earlier, to deflate the output and improve accuracy of the data,” Saurabh Garg, secretary in the Ministry of Statistics and Programme Implementation, said in an interview. The practice will continue until a revised WPI series is released, which is expected shortly, he said.