K. S. Lal, in his book Growth of Muslim Population in Medieval India, claimed that between 1000 and 1500 the Indian population decreased by 30 million,[241] but stated his estimates were tentative and did not claim any finality.[242][243][244] His work has come under criticism by historians such as Simon Digby (SOAS, University of London) and Irfan Habib for its agenda and lack of accurate data in pre-census times.[245][246] Different population estimates by economics historians Angus Maddison and Jean-Noël Biraben also indicate that India's population did not decrease between 1000 and 1500, but increased by about 35 million during that time.[247][248] The Indian population estimates from other economic historians including Colin Clark, John D. Durand and Colin McEvedy also show there was a population increase in India between 1000 and 1500.[249][250]