Promoter ownership in India's top 500 companies fell to an all-time low of 49.5% in the March quarter as rich share valuations and strong investor appetite prompted several founders to sell a portion of their stakes in the past year. Non-banking finance companies, telecom, electronic manufacturing services (EMS) companies and public sector banks saw the biggest decline in promoter stakes in the fourth quarter from the previous one, according to Motilal Oswal Financial Services.