New Delhi, Aug. 26 -- In an economy as vast as India's, timing is everything. Policymakers need to know not just what is happening, but when. Yet, our most important measure of economic performance, gross domestic product (GDP), has a timeliness of two months to one year. Quarterly GDP figures arrive two months after the period they pertain to. By then, the ground reality may already have changed.

What if we could track the economy in near real time, with the same speed and detail that financial markets track stock prices? The data already exists; the goods and services tax (GST) system is a gold mine. It's time to tap this opportunity.

From tax collection to economic nowcasting: When GST was rolled out in 2017, it replaced a maze of ce...