the decades following India's independence due to steep population increases and a rise in militant trade-unionism, which included frequent strikes that were backed by left-wing parties. From the 1960s to the late 1990s, several factories were closed and businesses relocated. The lack of capital and resources added to the depressed state of the city's economy and gave rise to an unwelcome sobriquet: the "dying city". The city's fortunes improved after the Indian economy was liberalised in the 1990s and changes in economic policy were enacted by the West Bengal state government. Recent estimates of the economy of Kolkata's metropolitan area have ranged from $150 to $250 billion (PPP GDP), and have ranked it third-most productive metro area of India. Flexible production has been the norm in Kolkata, which has an informal sector that employs more than 40% of the labour force. One unorganised group, roadside hawkers, generated business worth 87.72 billion ( 2 billion) in 2005. , around 0.81% of the city's workforce was employed in the primary sector (agriculture, forestry, mining, etc.); 15.49% worked in the secondary sector (industrial and manufacturing); and 83.69% worked in the tertiary sector (service industries). , the majority of households in slums were engaged in occupations belonging to the informal sector; 36.5% were involved in servicing the urban middle class (as maids, drivers, etc.) and 22.2% were casual labourers. About 34% of the available labour force in Kolkata slums were unemployed. According to one estimate, almost a quarter of the population live on less than 27 rupees (equivalent to 45 US cents) per day. Major manufacturing companies in the city are Alstom, Larsen & Toubro, Fosroc, Videocon. As in many other Indian cities, information technology became a high-growth sector in Kolkata starting in the late 1990s; the city's IT sector grew at 70% per annum—a rate that was twice the national average. The 2000s saw a surge of investments in the real estate, infrastructure, retail, and hospitality sectors; several large shopping malls and hotels were launched. Companies such as ITC Limited, CESC Limited, Exide Industries, Emami, Eveready Industries India, Lux Industries, Rupa Company, Berger Paints, Birla Corporation, Britannia Industries and Purushottam Publishers are headquartered in the city. Philips India, PricewaterhouseCoopers India, Tata Global Beverages, and Tata Steel have their registered office and zonal headquarters in Kolkata. Kolkata hosts the headquarters of three major public-sector banks: Allahabad Bank, UCO Bank, and the United Bank of