Industrialist Mukesh Ambani was today named India's richest for ninth year in a row with a net worth of $18.9 billion even as his wealth dipped by $4.7 billion in a year, while e-commerce giant Flipkart's founders made their debut on the country's top 100 rich list.As per Forbes magazine's latest India rich list released on Wednesday, Mr Ambani was followed by Sun Pharma's Dilip Shanghvi as second richest with a net worth of $18 billion, while Wipro's Azim Premji retained his third place with $15.9 billion.Flipkart's co-founders Sachin and Binni Bansal made their debut at 86th position with a net worth of $1.3 billion each.The combined wealth of India's 100 richest persons remained largely unchanged at $345 billion, as compared to $346 billion in 2014, Forbes said.The magazine said the Indian economy was estimated to grow at 7 per cent this year, but the wealth of many of India's 100 richest have gone down due to decline in the stock markets and depreciation in rupee value over the past one year.As many as 10 of them saw their net worth dip by over $1 billion each in one year, including Lakshmi Mittal, whose net worth dipped to $4.6 billion (ranked 8th with $11.2 billion). His rank also slipped three places.At the same time, many of the billionaires also saw their net worth rise further.The list saw as many as 12 newcomers including Flipkart's founders and low-cost airline IndiGo's co-founder Rakesh Gangwal who has debuted at 70th position with a net worth of $1.6 billion ahead of his company's IPO.Mr Gangwal's partner Rahul Bhatia has moved up 12 positions to 38th with a net worth of $2.4 billion.The biggest gainer was vaccine maker Serum's Cyrus Poonawalla whose wealth rose from $6.2 billion to $7.9 million, pushing his rank to the 9th position.Forbes said the minimum threshold for making it to the list has increased from $1 billion to $1.1 billion in 2015.In the top ten, Hinduja brothers were ranked 4th with $15.9 billion, followed by Pallonji Mistry at $14.7 billion, Shiv Nadar ($12. 9 billion), Godrej family ($11.4 billion), Lakshmi Mittal (11.2 billion), Cyrus Poonawala ($7.9 billion) and Kumar Mangalam Birla ($7.8 billion).Forbes said the list was compiled using shareholding and financial data obtained from families and individuals, stock exchanges, analysts and regulators.The ranking lists family fortunes including those shared among extended familes such as in the case of Godrej and Bajaj families, while public fortunes were calculated on the basis of share price and exchange rates as on September 11.The privately held companies were valued on the basis of their peer group companies that are publicly listed.