Although media freedom in Hong Kong is theoretically guaranteed by a bill of rights, the perceived freedom of the Hong Kong media according to the World Press Freedom Index ranks 61st out of 180 countries in 2014, having slid from 18th place in 2002. Concerns have been brought about by a number of factors and high-profile incidents affecting the media. Pundits and journalists alike have been alarmed at the erosion of journalists' ability to report the news in an objective manner. Journalists have complained about sensitive news stories critical of the government that they have been under undisguised pressure to change or soften. There has also been pressure on organisations including major financial institutions to pull advertising from newspapers that take a pro-democracy or anti-government stance, and the brazen attack on a respected newspaper editor; All told, the incidence of censorship, political pressure to self-censor and intimidation is increasing, according to PEN American Center and the International Federation of Journalists. The Hong Kong Journalists Association noted that there were at least 28 attacks on journalists covering the Umbrella Revolution. The aggressive moves made by publishing houses controlled by Sino United Publishing against independent publishers particularly since the 2014 protests, the unexplained disappearance in 2015 of four individuals linked to an independent publisher of sensitive books, as well as the acquisition of Hong Kong's newspaper of record by Alibaba Group all increased fears of political encroachment on press freedom by parties closely linked to the communist regime.