The population density in Hong Kong, already the highest in the world in some districts, is set to go even higher. Under a proposal before the government, the plot ratio - the total built area of a development divided by the total site area - is to be increased by 20 per cent or more in some urban areas and new towns, which will raise living density above the maximum allowable in housing developments in the world's major cities. The plot ratio for Hong Kong's high-rise residential developments in urban districts ranges from five to 10 times, according to Thomas Lam, head of research and consultancy for Greater China at property consultancy Knight Frank. Plot ratios, also known elsewhere in the world as floor area ratios or floor space ratios, are tools employed by urban planners to control development intensity. "Hong Kong's ratio is similar to that of New York's downtown district, which has a floor area ratio of between six to 10 times," Lam said. But it is higher than London's ratio, which ranges from as low as one to as high as six times; and Shanghai's 1.6 to 2.5 times. Singapore, a long-time rival of Hong Kong for attracting businesses, has a low plot ratio of 2.2 to four times. While admitting that "exact" comparisons of plot ratios or floor area ratios was not possible, since the development intensity was calculated in different ways in different cities, Lam noted that the government of Singapore tended to favour lower development intensities to enhance the quality of living spaces, unlike the policy trend in Hong Kong. He voiced concerns that Hong Kong's overworked public transport network and power utilities might struggle to cope with an even higher population density. The proposal to increase development intensity was announced by Chief Executive Leung Chun-ying in his second policy address speech on January 15. Under the proposal, the government is considering increasing the plot ratio of sites at medium and low-density locations in urban areas and new towns by 20 per cent. In some cases ratios on existing buildings that were only three storeys high may be relaxed to allow six storeys, Secretary for Development, Paul Chan Mo-po noted in his blog last month. Chan said in the blog that the government was aware of the concerns created by the proposed increases in living density and would take into account the circumstances and considerations of individual sites to ensure the provision of adequate transport infrastructure, utilities, services, and community facilities. Kim Chan Kim-on, a fellow at the Hong Kong Institute of Planners, said the plan to raise the plot ratio was the most readily achievable way to increase housing supply in the short-term aside from land reclamation or development in country parks. He said the negative effects of density could be mitigated by the design and layout of developments, and the creation of open spaces and traffic and community facilities. For example, more sky gardens could be built in ways to create a sensation of less crowding, Chan said.