Scientists have identified two "natural experiments" in Assam and Uttar Pradesh that they believe prove a fatal design defect in the Special Intensive Revision (SIR) of voter lists. The SIR's mandatory enumeration forms and proof of citizenship requirements are cited as problematic. In Assam, a revised draft voter list led to concerns, while UP panchayat elections also provided data. Researchers suggest that removing these two elements from the SIR process would prevent mass disenfranchisement, as demonstrated by the outcomes in these cases.