The combined market valuation of top seven Sensex companies tanked by a whopping Rs 1 lakh crore in the past week, with TCS, ONGC and RIL taking the steepest hit. The combined wealth erosion of these top seven Sensex firms, which also include SBI, HDFC Bank, Infosys and ICICI Bank, was Rs 1,02,431.31 crore. The total market value of all these seven firms stood at Rs 20.38 lakh crore in the week before. The Sensex concluded the week at 27,350.68, disclosing a sharp fall of 1,107.42 points of 3.89 per cent — the worst weekly drop since December 2011.