Banking in Australia is notable by the small number of large banks in the market. Much of this concentration is the result of bank acquisitions. English, Scottish and Australian Bank was acquired by the ANZ Bank in 1970. In 1982, Bank of New South Wales merged with the Commercial Bank of Australia to form Westpac. There were many other bank mergers and acquisitions throughout Australia's banking history. The boom and bust of the 1980s was a turbulent period for banks, with some establishing leading market positions, while others being absorbed by the larger banks. Beginning in the 1980s, several building societies sought to convert to banks, but were required to demutualise before they were permitted to do so. This included NSW Building Society, which became Advance Bank, St.George, Suncorp, Metway Bank, Challenge Bank, Bank of Melbourne and Bendigo Bank. A change in regulations allowed building societies and credit unions to become banks without having to demutualise, and several including Heritage Bank have converted since 2011 while retaining their status and structure as mutual organisations.