Protest organisers inflating the numbers to push their cause could explain growing discrepancies in turnout estimates - between organisers, police and academics - for mass rallies, says one academic. The remark, by University of Hong Kong social administration professor Paul Yip Siu-fai, came after the release of wildly varying figures for the January 1 protests - both for and against Chief Executive Leung Chun-ying. Yip said that since academics and the police had not made any change to their methods of assessing the turnout, the discrepancies might be "because organisers have puffed up the figures more and more". "Protests are supposed to be about expressing demands. A larger turnout may help organisers boost their bargaining power, but if they are excessively overblown it may make the estimate meaningless," said Yip, who has been doing turnout estimates on the July 1 march since 2003. The Civil Human Rights Front claimed some 130,000 people took to the streets on Tuesday calling for Leung to step down. That was five times the police estimate. The University of Hong Kong's Public Opinion Programme put the figure at between 30,000 and 33,000. For the July 1 march in 2003, its turnout estimate of 500,000 was just 1.4 times the police figure. The Public Opinion Programme number was 429,000 to 502,000, while Yip's estimate was between 220,000 and 250,000. Big discrepancies between the figures were also seen for the pro-Leung camp on Tuesday. The Hong Kong Island Federation said 60,000 people joined its January 1 march from Central to the government headquarters in Admiralty - 7.5 times the police estimate. Voice of Loving Hong Kong put its rally turnout at 2,500 - five times the police figure. Jackie Hung Ling-yu, convenor of the Civil Human Rights Front, which has organised a July 1 march since 2003 and the January 1 anti-Leung rally this year, declined to comment on the claim they inflated the turnout estimate. Hung said different methods were used to assess turnout - the Front counted each protester passing certain points - Causeway Bay, Wan Chai and Admiralty - and adjusted the data to account for those who might have joined the march midway. Chan Yung, the chairman of the New Territories Association of Societies, a co-organiser of the pro-Leung march, said the turnout figures were all estimates and there was no authoritative one. Public Opinion Programme senior data analyst Tai Chit-fai told RTHK yesterday its estimate of up to 33,000 people taking part in Tuesday's anti-government rally was based on a headcount conducted by 15 people at a flyover on Arsenal Street. It was enlarged to take into account the fact some protesters may have left early. "From data collected during last year's protest [on July 1], 72 per cent of those who joined the rally walked past the booth on [Arsenal Street]," he said.