One in five Hongkongers in employment have only part-time or casual work, according to a study funded by the Central Policy Unit and the Research Grants Council. The figure suggests employers prefer using non-full-time staff to reduce operating costs. The latest statistics are among interim findings of a five-year study begun in 2009 by the University of Science and Technology's Centre for Applied Social and Economic Research. Some 3,511 of its respondents were in work. The study defines marginal employment as part-time or casual jobs, or working fewer than 30 hours a week. Although 20 per cent of the respondents were marginally employed, the survey found that, on average, the workers put in 47 hours a week. Among those in marginal jobs, 36 per cent had received only primary school education or less; another 30 per cent had been educated only up to junior forms in secondary schools. About 40 per cent had non-skilled jobs such as cleaning, while 25 per cent worked in service industries or sales. Workers in marginal employment made about HK$11,000 a month, while the full-time workers polled made less than HK$16,000 a month. More than 80 per cent of those in marginal employment did not enjoy any welfare benefits from employers. The centre's director, Wu Xiaogang, said a substantial proportion of young people were in marginal employment and could not find full-time jobs with good prospects. "Obviously, this has become a major source of grievances in the community," he said. Ng Wai-tung, a committee organiser at the Society for Community Organisation, said those who took up part-time and casual jobs were mostly homeless people or those undergoing rehabilitation for drug addiction. "Many bosses prefer hiring part-time or casual workers because they can avoid offering employment benefits such as statutory holidays or paying Mandatory Provident Fund contributions," he said.