<Tr> <Td_colspan="14"> Source #2: NOAA (humidity, sun 1971--1990) </Td> </Tr> <P> Air pollution is a major issue in Mumbai . According to the 2016 World Health Organization Global Urban Ambient Air Pollution Database, the annual average PM2. 5 concentration in 2013 was 63 μg / m, which is 6.3 times higher than that recommended by the WHO Air Quality Guidelines for the annual mean PM2. 5 . The Central Pollution Control Board for the Government of India and the Consulate General of the United States, Mumbai monitor and publicly share real - time air quality data . </P> <P> Mumbai is India's largest city (by population) and is the financial and commercial capital of the country as it generates 6.16% of the total GDP . It serves as an economic hub of India, contributing 10% of factory employment, 25% of industrial output, 33% of income tax collections, 60% of customs duty collections, 20% of central excise tax collections, 40% of India's foreign trade and ₹ 4,000 crore (US $610 million) in corporate taxes . Along with the rest of India, Mumbai has witnessed an economic boom since the liberalisation of 1991, the finance boom in the mid-nineties and the IT, export, services and outsourcing boom in the 2000s . Although Mumbai had prominently figured as the hub of economic activity of India in the 1990s, the Mumbai Metropolitan Region is presently witnessing a reduction in its contribution to India's GDP . </P> <P> As of 2016 recent estimates of the economy of the Mumbai Metropolitan Region have ranged from $151 to $368 billion (PPP metro GDP) ranking it either the most or second-most productive metro area of India . Many of India's numerous conglomerates (including Larsen & Toubro, State Bank of India (SBI), Life Insurance Corporation of India (LIC), Tata Group, Godrej and Reliance), and five of the Fortune Global 500 companies are based in Mumbai . This is facilitated by the presence of the Reserve Bank of India (RBI), the Bombay Stock Exchange (BSE), the National Stock Exchange of India (NSE), and financial sector regulators such as the Securities and Exchange Board of India (SEBI). </P>

Why mumbai is called financial capital of india