balance shown on the prior month's statement. Later, it was decided to use "average daily balance" which resulted in increased revenue for the issuers by calculating the number of days each purchase was included on the prior month's statement. Several years later, "new average daily balance"—in which transactions from previous and current billing cycles were used in the calculation—was introduced. By the early 1980s, many issuers introduced the concept of the annual fee as yet another revenue enhancer. IPO and restructuring On October 11, 2006, Visa announced that some of its businesses would be merged and become a publicly traded company, Visa Inc. Under the IPO restructuring, Visa Canada, Visa International, and Visa USA were merged into the new public company. Visa's Western Europe operation became a separate company, owned by its member banks who will also have a minority stake in Visa Inc. In total, more than 35 investment banks participated in the deal in several capacities, most notably as underwriters. On October 3, 2007, Visa completed its corporate restructuring with the formation of Visa Inc. The new company was the first step towards Visa's IPO. The second step came on November 9, 2007, when the new Visa Inc. submitted its $10 billion IPO filing with the U.S. Securities and Exchange Commission (SEC). On February 25, 2008, Visa announced it would go ahead with an IPO of half its shares. The IPO took place on March 18, 2008. Visa sold 406 million shares at US$44 per share ($2 above the high end of the expected $37–42 pricing range), raising US$17.9 billion in what was then the largest initial public offering in U.S. history. On March 20, 2008, the IPO underwriters (including JP Morgan, Goldman Sachs & Co., Bank of America Securities LLC, Citi, HSBC, Merrill Lynch & Co., UBS Investment Bank and Wachovia Securities) exercised their overallotment option, purchasing an additional 40.6 million shares, bringing Visa's total IPO share count to 446.6 million, and bringing the total proceeds to US$19.1 billion. Visa now trades under the ticker symbol "V" on the New York Stock Exchange. Visa Europe Visa Europe Ltd. was a membership association and cooperative of over 3,700 European banks and other payment service providers that operated Visa branded products and services within Europe. Visa Europe was a company entirely separate from Visa Inc. having gained independence of Visa International Service Association in October 2007 when Visa Inc.