The country's top 10 companies have witnessed an erosion of about Rs 72,000 crore (Rs 720 billion) from their market capitalisation in a week, with Reliance Industries' [Get Quote] valuation again dipping below the Rs 2,00,000-crore (Rs 2,000 billion) mark.

Meanwhile, IT bellwether Infosys [Get Quote] and BHEL defied trend and together added Rs 4,085 crore (Rs 40.85 billion) to their valuation in a week.

During the week, the market capitalisation of top 10 firms -- comprising five each from public and private sectors -- witnessed an erosion by Rs 71,793 crore (Rs 717.93 billion) in their valuation to Rs 10,20,313 crore (Rs 10,203.13 billion).

The market capitalisation of the 10 companies as on January 2 was at Rs 10,92,106 crore (Rs 10,921.06 billion).

During the week, the Mukesh Ambani-led firm's valuation dipped to Rs 1,81,152 crore (Rs 1,811.52 billion), an erosion of Rs 20,908 crore (Rs 209.08 billion) during the week's time. The corporate behemoth had a market capitalisation of Rs 2,02,060 crore (Rs 2,020.60 billion) in the week ago period.

The company also witnessed a 10 per cent plunge in its share price during the week to settle at Rs 1,151.05 on Friday.

The shuffling in the premier category of these 10 coveted companies saw state-run NMDC falling out of it after losing Rs 16,711.21 crore (Rs 167.112 billion) in a week, while BHEL taking its place at the seventh spot. Also Infosys climbed up to the eighth spot from 10th last week. Hindustan Unilever entered the coveted club at the 10th place.

IT major Infosys Technologies was added Rs 3,673 crore (Rs 36.73 billion) to its market capitalisation and BHEL gained Rs 411 crore (Rs 4.11 billion) during the week.

While Infosys surged as much as 6 per cent during the week to Rs 1,195.10, BHEL also advanced a marginal 0.59 per cent to Rs 1,416.65 at the end of trade on Friday.

State-run NTPC, which replaced ONGC [Get Quote] as the most valued PSU firm two weeks back and lost Rs 4,865 crore (Rs 48.65vbillion) last week, retained its position with market cap of Rs 1,468,52 crore (Rs 1,468.52 billion) on Friday.

Meanwhile, ONGC retained the third position with a market valuation of Rs 1,43,411 crore (Rs 1,434.11 billion), a decline of Rs 2,042.62 crore (Rs 20.426 billion) over the week-ago period.

Private sector telecom services provider Bharti Airtel [Get Quote] lost Rs 12,841 crore (Rs 1,284.10 billion) in a week and state-owned MMTC's valuation declined to Rs 9,910 crore (Rs 99.10 billion).

The country's largest lender, SBI [Get Quote], witnessed an erosion of Rs 7,244 crore (Rs 72.44 billion) in its valuation and diversified conglomerate ITC witnessed an erosion of Rs 1,716 crore (Rs 17.16 billion) from its market cap.

FMCG major HUL made its way to the top 10 firms' club despite losing Rs 16,350 crore (Rs 163.50 billion).

Apart from top 10 companies, the week also saw beleaguered IT major Satyam's [Get Quote] valuation declining by over Rs 10,350 crore (Rs 103.50 billion).

Its scrip plunged nearly 90 per cent to Rs 23.85 on Friday last, from Rs 177.55 in the week-ago period. Its m-cap stood at Rs 1,607 crore (Rs 16.07 billion), down from Rs 11,963 crore (Rs 119.63 billion) a week ago.

Besides, private sector banking giant ICICI Bank [Get Quote] saw an erosion of Rs 1,820 crore (Rs 18.20 billion)  to its valuation. While, the second largest private sector lender HDFC Bank [Get Quote] lost Rs 149 crore (Rs 1.49 billion).

ICICI Bank market cap stood at Rs 50,637 crore (Rs 506.37 billion), while HDFC Bank was at Rs 43,037 crore (Rs 430.37 billion) at the end of Friday.

RIL, the numero-uno in the list of the most valued firms, is followed by NTPC (Rs 1,46,852 cr0re), ONGC (Rs 1,43,411 crore), Bharti Airtel (Rs 1,20,945 crore), MMTC (Rs 90,822 crore), SBI (Rs 77,195 crore), BHEL (Rs 69,348 crore), Infosys (Rs 68,436 crore), ITC (Rs 63,927 crore) and HUL (Rs 58,226 crore).