Indian stock market has been under tremendous pressure in recent weeks, primarily due to global economic worries, and its overall valuation has fallen by an estimated USD 200 billion so far in the current quarter, beginning July 1. Tata group, a global steel magnate and one of India\'s largest firms in terms of market wealth has taken a hit of over USD 20 billion in its market valuation since July. The loss suffered by Ratan Tata-led group accounts for over 10 per cent of the overall loss in the market and is also higher than a cumulative erosion of USD 15 billion from the stock wealth of two Ambani groups. While Mukesh Ambani-led Reliance Industries group for long the darling of Indian investors, was knocked off its four-year long perch as the country\'s most valuable company, as fears over slowing gas production dragged its stock down almost 30% this year and led to the first full day of trade with Coal India on top. It has lost close to USD 9.89 billion. Business houses having suffered significant erosion in their valuation also include Vedanta, Adani, ICICI, Infosys, Wipro and Jindal groups.The Indian market\'s total valuation has fallen from USD 1.53 trillion at the beginning of this quarter to USD 1.33 trillion currently.