The GDP combat sport

The GDP figure is only an estimate. Statisticians, like those elsewhere, work with samples, surveys, company accounts, tax returns, and administrative data. Where information is missing, they infer. Where better information subsequently turns up, they revise. Quarterly estimates involve still more inference. India's problem is more acute than that of many rich countries. The formal economy is increasingly well documented, thanks to goods and services tax (GST), digital payments, and eway bills. But millions of small firms and workers still inhabit the statistical penumbra. Nor would India be the first country to have trouble measuring itself. China's GDP figures have for years attracted suspicion for their remarkable smoothness. Advanced economies too, with all their statistical machinery, revise GDP estimates.