India's Slow Urbanisation in One Number: The Urban–Rural Growth Difference, an Exact Identity, and India's Place on the Cross-Country Income Curve, 1960–2025

The pace of urbanisation is usually described by the change in the urban share, which mechanically slows as the share approaches its limits. I use an exact alternative: the change in the log-odds of the urban share equals the urban population growth rate minus the rural growth rate (the urban–rural growth difference, URGD). The identity holds in World Bank data to within 1.13e-05 on average across 13,462 country-years, with a correlation of 0.999997. India's urban share rose from 17.93% in 1960 to 35.69% in 2025. Its URGD was 1.708% a year in 1960–1980, fell to 1.089% in 1980–2000, and was 1.399% in 2015–2025, against 3.833% for China and 3.353% for Nigeria over the same decade. At the recent rate India would reach a 50% urban share in about 2067. On a cross-country regression of the log-odds of the urban share on log GDP per capita at purchasing power parity, India's urban share in 2023 (35.1%) is well below the 55.6% predicted for its income, ranking 29th lowest of 188 economies; the gap has widened since 1995. Part of this gap reflects India's narrow statutory definition of urban areas.