The 2010 Blue Book of Religions, produced by the Institute of World Religions at the Chinese Academy of Social Sciences, a research institution directly under the State Council, estimates Catholics in China to number about 5.7 million. This Chinese government estimate only includes members of the Catholic Patriotic Association (CPA). It does not include un-baptized persons attending Christian groups, non-adult children of Christian believers or other persons under age 18, and unregistered Christian groups. The Holy Spirit Study Centre in Hong Kong, which monitors the number of Chinese Catholic members, estimated in 2012 that there were 12 million Catholics in both branches of the Catholic Church. The Pew Research Center estimates in 2011 there are nine million Catholics on the mainland, 5.7 million of whom are affiliated with the CPA. Hebei Province has the largest Catholic Christian population in China, with 1 million Church members according to the local government. Generally, Catholic institutions are dominant in North and Central regions of China. Hong Kong and Macau The Catholic Church is allowed to operate freely in Macau and Hong Kong. In fact, Donald Tsang, the former Chief Executive of Hong Kong, is a Catholic. Pope John Paul II was, however, denied a visit (which was deemed "inappropriate") to Hong Kong in 1999, by then Chief Executive, Tung Chee Hwa, who was in office from 1997 to 2005, a decision many believe was made under pressure from the central PRC government. The two territories are organized into the Diocese of Hong Kong and the Diocese of Macau. Diplomatic relations with the Vatican The issue of Sino-Vatican relations has been a highly contentious one and often difficult for both sides (see below). The Catholic Patriotic Association (CPA) is a division of China's Religious Affairs Bureau, and has oversight over China's Catholics. According to at least one source, however, China's Catholics, including its clergy and religious sisters, are no longer required to be members of the CPA. By 2007, the Vatican had indicated on multiple occasions that it desired to establish full diplomatic relations with China, and would be willing to move its embassy from Taiwan to mainland China if necessary. A major obstacle between the two sides remained the Catholic doctrine that only the pope can appoint bishops of the Church. Bishops in the CPA were government-appointed, a frequent aggravating factor in Sino-Vatican relations. Some, including Hong Kong Cardinal Joseph Zen, saw the