New Delhi, Sept. 3 -- India's latest GDP data has drawn widespread scrutiny since the figures were released on Monday. Official statistics said India's GDP growth rate was 7.8% in April-June, which was hailed as a "Herculean feat" by Prime Minister Narendra Modi, but former finance secretary Subhash Garg claimed it was only 2.6%.

In reality, 7.8% is not the final figure and 2.6% isn't the correct one. Scepticism over the numbers stems from two factors: the overestimation of GDP under the previous series and high growth figures failing to translate into widespread prosperity.

Let's start with the official print. Quarterly estimates, released about two months after the end of a quarter, are often based on limited data. As more data become...