Today we focus on the recently released Q1 GDP figure. It’s created a storm of controversy. So we ask is the 7.8% figure credible or, as former finance secretary Subhash Chandra Garg has said, should it be 2.6%? Beyond that why do we frequently overestimate GDP growth? And how accurately are we calculating GDP? My guest is the one man who should know the answers to these questions, India’s former chief statistician, Pronab Sen.