Macau has become one of the most attractive places on Earth to live, if measured by its net migration rate. The former Portuguese enclave ranks No1 in the world in terms of the difference of immigrants and emigrants per 1,000 residents, according to the latest ranking by the US Central Intelligence Agency. The online CIA World Factbook, updated this month, shows that Macau had a net migration rate of 26.21 per 1,000 residents last year to top a list of 173 countries and regions. Macau jumped from 25th place in last year's rankings. Economist and gaming analyst Zeng Zhonglu said mainland workers accounted for the bulk of Macau's influx of migrants. The city of 557,400 residents had more than 100,000 imported workers at the end of September, although the number fell slightly to 95,574 by the end of November. Workers from Hong Kong and Southeast Asia also pushed up the city's net migration rate. Professor Zeng, of Macau Polytechnic Institute, said the large number of migrant workers benefited the city's economy by filling a labour shortage and boosting consumption. 'The workers are needed to drive Macau's economic growth, and their spending boosts local housing and retail sectors.' But he said the army of migrants also strained Macau's infrastructure, slowing traffic and causing human bottlenecks at ports of entry. Paul Yip Siu-fai, a Hong Kong population expert who has studied Macau's social development, said the influx of migrant workers had left locals embittered. The University of Hong Kong professor said newcomers had been driving up living costs in Macau and taken jobs from locals. 'Many locals are left with resentment that they are unable to benefit from the city's economic growth,' he said. 'The government must address their concerns.' Last year Professor Yip took part in a research project on Macau's sustainable development. He said it needed to step up education and job training to improve locals' competitiveness in the labour market. The CIA World Factbook ranks Hong Kong 27th in net migration, with a total of 4.55 per 1,000 residents. Hong Kong was 24th a year ago. The mainland was 99th, with minus 0.39 per 1,000 residents. Canada, known for attracting immigrants, ranks 21st with 5.62 per 1,000 residents. High levels of migration can cause problems such as increasing unemployment and potential ethnic strife, the CIA World Factbook said. Professor Zeng said Macau's inflow of migrant workers may slow this year with the casino industry taking a hit amid the financial crisis. Still, casino operator Melco Crown Entertainment plans to hire around 5,000 locals and 2,000 non-locals for its City of Dreams resort, due to open this year.