Melbourne has a highly diversified economy with particular strengths in finance, manufacturing, research, IT, education, logistics, transportation and tourism. Melbourne houses the headquarters for many of Australia's largest corporations, including five of the ten largest in the country (based on revenue), and four of the largest six in the country (based on market capitalisation) (ANZ, BHP Billiton (the world's largest mining company), the National Australia Bank and Telstra), as well as such representative bodies and think tanks as the Business Council of Australia and the Australian Council of Trade Unions. Melbourne's suburbs also have the Head Offices of Wesfarmers companies Coles (including Liquorland), Bunnings, Target, K-Mart & Officeworks. The city is home to Australia's largest and busiest seaport which handles more than $75 billion in trade every year and 39% of the nation's container trade. Melbourne Airport provides an entry point for national and international visitors, and is Australia's second busiest airport.[citation needed]