Co. acquired it. After retiring from politics in 1964, former Prime Minister of the United Kingdom, Harold Macmillan, grandson of co-founder Daniel, became chairman of the company, serving until his death in December 1986. He had been with the family firm as a junior partner from 1920 to 1940 (when he became a junior minister), and from 1945 to 1951 while he was in the opposition in Parliament. The German Holtzbrinck Publishing Group purchased the company in 1999. 21st century Pearson acquired the Macmillan name in America in 1998, following its purchase of the Simon & Schuster educational and professional group (which included various Macmillan properties). Holtzbrinck purchased it from them in 2001. McGraw-Hill continues to market its pre-kindergarten through elementary school titles under its Macmillan/McGraw-Hill brand. The US operations of Holtzbrinck Publishing changed its name to Macmillan in October 2007. Its audio publishing imprint changed its name from Audio Renaissance to Macmillan Audio, while its distribution arm was renamed from Von Holtzbrinck Publishers Services to Macmillan Publishers Services. Pan Macmillan purchased Kingfisher, a British children's publisher, from Houghton Mifflin in October 2007. Roaring Brook Press publisher Simon Boughton would oversee Kingfisher's US business. By some estimates, as of 2009, e-books account for three to five per cent of total book sales, and are the fastest growing segment of the market. According to The New York Times, Macmillan and other major publishers "fear that massive discounting [of e-books] by retailers including Amazon, Barnes & Noble and Sony could ultimately devalue what consumers are willing to pay for books." In response, the publisher introduced a new boilerplate contract for its authors that established a royalty of 20 per cent of net proceeds on e-book sales, a rate five per cent lower than most other major publishers. Following the announcement of the Apple iPad on 27 January 2010—a product that comes with access to the iBookstore—Macmillan gave Amazon.com two options: continue to sell e-books based on a price of the retailer's choice (the "wholesale model"), with the e-book edition released several months after the hardcover edition is released, or switch to the agency model introduced to the industry by Apple, in which both are released simultaneously and the price is set by the publisher. In the latter case, Amazon.com would receive a 30 per cent commission. Amazon responded by pulling all Macmillan books, both electronic and physical, from their website (although affiliates