According to Forbes magazine, Chennai is one of the fastest growing cities in the world. It has a diversified economic base anchored by the automobile, software services, hardware manufacturing, healthcare and financial services industries. As of 2000, the city's total personal income was 12,488.83 crores, making up 10.9% of the total income of Tamil Nadu. In 2001, the total workforce in Chennai was about 1.5 million, which was 31.79% of its population. According to the 1991 census, most of the city's workforce was involved in trade (25.65%), manufacturing (23.52%), transportation (10.72%), construction (6.3%) and other services (31.8%). Chennai metropolitan area accounts for over 75% of the sales tax revenue in the state. According to the CII, Chennai is estimated to grow to a $100-billion economy, 2.5 times its present size, by the year 2025.
The city is base to around 30% of India's automobile industry and 35% of its auto components industry. A large number of automotive companies including Hyundai,Ford, BMW, Mitsubishi, Nissan, Renault, Komatsu, The TVS Group (TVS Electronics and TVS Motors), Ashok Leyland, Daimler Trucks, TI Cycles of India, TAFE Tractors, Royal Enfield, Caterpillar Inc., Caparo, Madras Rubber Factory (MRF), Michelin and Apollo Tyres have or are in the process of setting up manufacturing plants in and around Chennai. The Heavy Vehicles Factory at Avadi produces military vehicles, including India's main battle tank: Arjun MBT. The Integral Coach Factorymanufactures railway coaches and other rolling stock for Indian Railways. The Ambattur-Padi industrial zone houses many textile manufacturers, and an SEZ for apparel and footwear manufacture has been set up in the southern suburbs of the city. Chennai contributes more than 50% of India's leather exports.
Many software and software services companies have development centres in Chennai, which contributed 14% of India's total software exports of 144,214 crores during 2006–07, making it the second-largest exporter, by city, of software in the country, behind Bangalore. Major software companies have their offices set up here, with some of them making Chennai their largest base. Prominent financial institutions, including the World Bank, Standard Chartered Bank and Citibank have back officeoperations in the city. Chennai is home to two large national level commercial banks and many state level co-operative banks, finance and insurance companies. Telecom and Electronics manufacturers based in and around Chennai include Nokia, Nokia Siemens, Motorola, Dell, Samsung, Foxconn and Siemens among others. Telecom giants Ericsson and Alcatel-Lucent, pharmaceuticals giant Pfizer and chemicals giant Dow Chemicals have research and development facilities in Chennai. TICEL bio-tech park and Golden Jubilee bio-tech park at Siruseri house biotechnology companies and laboratories. Chennai has a fully computerised stock exchange called the Madras Stock Exchange. Medical tourism is another important part of the city's economy with health care providers like Apollo Hospitals, Fortis Healthcare based in Chennai and also Chennai is considered to be the healthcare capital of India. The Tamil movie industry, the related Tamil Music industry and the Tamil television industry are also significant parts of Chennai's economy.
In the Inventory of World cities from the Globalization and World Cities Research Network, Chennai's level of network integration with other world cities is ranked as a "Gamma+", alongside cities such as Montreal, Nairobi, Bratislava, Panama City, Brisbane, Casablanca, Denver, Vancouver, Zagreb, Manama and Cape Town.