As of last year, Delhi may have overtaken Mumbai as the country's largest city in terms of population, as per a recent study. For over two decades now, the Census reports have pegged Mumbai as the country's biggest metropolitan area. But two demographers from the Washington DC-based Population Reference Bureau (PRB) have found that if the same definition for measuring the populations of Mumbai and Kolkata is applied to Delhi, then the national capital's estimated population for 2007 is much more.