Question: The Shapoorji Pallonji Group was headed by the man who had an estimated wealth of what figure, as of September 2016?
Context: The Shapoorji Pallonji Group (SP Group) is an Indian business conglomerate in India with interests in construction, real estate, textiles, engineering goods, home appliances, shipping, publications, power, and biotechnology.  It was headed by Pallonji Mistry until 2012, when he announced his retirement and his son Shapoor Mistry took charge.  Shapoorji Pallonji is regarded as "one of India's most valuable private enterprises".  The promoters of the group are also the largest individual shareholders in Tata Sons, the holding company of the Tata Group.  The US$2.5 billion Shapoorji Pallonji Group have two listed companies, Forbes & Company Ltd. (), and Gokak Textiles.  Forbes was already listed when bought by Shapoorji Pallonji, though there was speculation in 2006 that group company Afcons Infrastructure would go public via an IPO. Pallonji Shapoorji Mistry (born 1929) is an Irish Indian construction tycoon and chairman of Shapoorji Pallonji Group.  According to "Forbes", his wealth is estimated to be US$16.9 billion as of September 2016.  With his 18.4% stake in Tata Sons, he is the single largest shareholder in India's largest private conglomerate Tata Group.  He is the chairman of the "Shapoorji Pallonji Group" through which he owns Shapoorji Pallonji Construction Limited, Forbes Textiles and Eureka Forbes Limited.  He is the former chairman of Associated Cement Companies.  Pallonji gave up his Indian citizenship in 2003 to obtain Irish nationality, because India does not yet allow dual nationality .  His son Cyrus was chairman of Tata Sons from November 2011 to October 2016.  A short biography of Mistry was written in a 2008 book by Manoj Namburu titled "The Moguls of Real Estate".  He was awarded the Padma Bhushan in January 2016 by the Government of India for his contributions in the field of trade and industry. Forbes & Company Ltd., the erstwhile Forbes Gokak Ltd. based in Mumbai, is the oldest registered company in India and one of the oldest in the world, which is in the business.  It was established in the year 1767, by a Scottish gentleman "John Forbes" Esq. of Aberdeenshire, Scotland.  Over the past few years, the management of the company moved from the Forbes family to the Campbells to the Tata Group and now finally to the well known Shapoorji Pallonji Group; leaders in infrastructure, construction and real estate businesses, amongst many others.  Forbes & Company Limited has three main businesses, namely: The Barakhambha Road (Hindi: बाराखम्भा मार्ग ) Metro Station is located on the Blue Line of the Delhi Metro.  It was constructed by the Shapoorji Pallonji Group. Shapoorji Mistry was an Indian businessman, and the founder of the Shapoorji Pallonji Group.  He was the father of Pallonji Mistry. Next Gen Publishing is an Indian publishing company.  It was created in 2005 by its parent companies Forbes Group, a subsidiary of Shapoorji Pallonji Group, and HDFC Bank.  Hoshang Billimoria was CEO of the newly created company. Eureka Forbes Ltd is a consumer goods company based in Mumbai, India.  It was founded in 1982 and is a part of the Shapoorji Pallonji Group. The Mumbai World Trade Centre at Cuffe Parade was built in 1970.  It consists of two towers, the "M Visvesaraya Industrial Research and Development Centre" (MVIRDC) and IDBI.  MRVDC was, at 156m, the tallest building in South Asia until the 2010 completion of The Imperial towers at Tardeo (252m).  It was built by the Shapoorji Pallonji Group. Srichand Parmanand Hinduja (born 28 November 1935) is an Indian-born British billionaire business magnate, investor, and philanthropist.  He is the primary shareholder and chairman of Hinduja Group of companies.  As of May 2017, together with his brother Gopichand he is the UK's richest man.  Since the 1990s, he has been consistently ranked among the UK and Asia's wealthiest people.  In May 2017, Hinduja topped the "Sunday Times" Rich List with an estimated wealth of GBP 16.2 billion ($21 billion).  Based on the rich list compiled by Asian Media & Marketing Group, Hinduja's wealth is estimated at GBP 19 billion ($24.7 billion).  The "Forbes" List in March 2016 ranked him and his brother GP as the world's 58th richest billionaire family with an estimated wealth of $16.4 billion. The Shapoorji Pallonji National Academy or National Cricket Academy is a cricket academy and training centre based at the Malahide Cricket Club Ground in Malahide, Dublin, Republic of Ireland.  The centre was sponsored by the Shapoorji Pallonji Group.
Answer: US$16.9 billion