A whopping Rs. 73,000 crore was eroded from the market capitalisation of seven of the top 10 firms last week and during the period the benchmark Sensex fell below the psychologically crucial 17,000-mark.

However, NMDC, Bharti Airtel and BHEL added Rs. 23,053.89 crore to their market valuation for the week ended January 23.

The country’s largest iron ore producer NMDC, which will come out with a follow-on public offer to divest 8.3 per cent, was the biggest gainer. It jumped to the third place from fourth in the list of top 10 companies going by their market valution. NMDC added Rs. 21,429.21 crore to its valuation to end the week at Rs. 2,11,120.28 crore.

State-run oil firm ONGC saw the biggest fall of Rs. 21,035.79 crore, bringing its its total valuation to Rs. 2,38,451.92 crore. ONGC reported a 23 per cent jump in third quarter profit at Rs. 3,053 crore.

Mukesh Ambani-led Reliance Industries, the biggest company by m-cap, also lost Rs. 18,421.28 crore. Its valution stood at Rs. 3,46,126.17 crore at the end of of the week.

The State-run power behemoth NTPC slipped to fourth place from third after losing Rs. 8,245.46 crore. Trading firm MMTC down by Rs. 8,733.75 crore is at the fifth place. Its total valuation declined to Rs. 1,83,461.49 crore.

Another PSU MMTC’s m-cap dipped to Rs. 1,75,675.25 crore.

Software giants TCS and Infosys Technologies together lost Rs. 13,053.11 crore.

TCS is at the sixth place at Rs. 1,47,788.17 crore and Infosys at Rs. 1,47,574.71 crore is at seventh place.

Country’s largest public sector lender SBI, eighth in the list, witnessed an erosion of Rs. 3,415.65 crore, bringing its total valution to Rs. 1,32,702.62 crore.

Private telecom services provider Bharti Airtel stood at ninth spot with a total valuation of Rs. 1,21,996.32 crore.

Bharti Airtel posted 2.3 per cent rise in third quarter profit at Rs. 2,210 crore.

Power equipment maker BHEL at tenth spot with a m-cap of Rs. 1,16,123.93 crore. The PSU’s declared a 35.67 per cent increase in profit at Rs. 1,072.5 crore for quarter ended December 31, 2009.

During the past week, the 30-share benchmark Sensex of the Bombay Stock Exchange saw a decline of nearly four per cent or 694.62 points during the week to close at 16,859.68 points at the end of Friday’s trade.