In one extreme case, almost 62 per cent of voters aged 66 to 70 cast their ballots in the last Legco polls, when the average turnout was 55.2 per cent. Only 42.3 per cent of voters aged between 18 and 20 cast their ballots that year.

Elderly electors are traditionally regarded as having a pro-establishment inclination. Last year the Post revealed how pro-Beijing parties helped residents of elderly homes to register as voters, subsequently ferried them to polling stations and allegedly told them who to vote for.

Political scientist Ivan Choy Chi-keung of Chinese University said young people were never core voters in Hong Kong, but he believed things might start to change this year.

He pointed to the New Territories East Legco by-election in February, where rising pro-independence leader Edward Leung Tin-kei, of Hong Kong Indigenous, raised eyebrows by securing more than 15 per cent of votes.

In that historic poll, the turnout of those aged below 40 surged drastically and contributed to one-third of total ballot papers.

“It might be too early to generalise what happened in New Territories East to the whole of Hong Kong as after all the constituency has the largest pool of young voters while Leung also has his own charisma,” Choy said.

“But with the emergence of new groups which advocate fresh agendas such as localism and self-determination, perhaps the young voters this year will be more motivated to cast their ballots.”

But Leung will not run next month. He is one of six young radicals who had their nominations invalidated by the Electoral Affairs Commission because of their advocacy of independence for Hong Kong.

While Choy said the pro-establishment camp might not have tried its best to mobilise voters in the by-election, he believed the bloc would step up its effort this time amid a sense of crisis.

According to the latest electoral roll, almost 47 per cent of the city’s voters were 36 to 60 years old, while young voters aged below 35 and elderly voters aged above 60 made up 24 per cent and 29.3 per cent of the pie respectively.

A large number of people were driven to register as voters following the pro-democracy sit-ins in 2014, but that surge was seen across the age spectrum and not limited to the young generation, who have often described the civil disobedience movement as their “political awakening”.

Meanwhile, the pan-democratic camp faces another challenge resulting from the steady influx of mainland Chinese immigrants allowed into Hong Kong under the one-way permit scheme, which allows 150 of them to settle in the city each day.

In a recent study in an academic journal, Hong Kong political scientists Stan Wong Hok-wui, Ma Ngok and Lam Wai-man used data analysis to prove a long-held assumption – that these immigrants tended to offer staunch support for the government.

“People who decide to move to an undemocratic place tend to be more tolerant towards an autocratic regime,” Ma explained.

The study found that two-thirds of pan-democratic supporters were Hong Kong natives, while 56 per cent of pro-Beijing backers were immigrants.

The researchers argued that the establishment could take advantage of the influx of mainland Chinese immigrants to counter-balance the rising democratisation demands of local people.

Additional reporting by Joyce Ng