BEIJING -- The number of overseas Chinese has reached 35 million, making it the largest migrant group in the world, according to a report by the Chinese Academy of Social Sciences (CASS).

The Report on International Politics and Security said that overseas Chinese have been living and working in 151 countries, with Australia, European and North American countries their main inhabited areas.

Overseas Chinese are usually employed in construction, farming and deforestation sectors or run their own businesses in retail, real estate and importing.

Some 460,000 migrants from the Chinese mainland settled down in the United States in the 1990s, doubling the total number of Chinese mainland migrants in the United States.

From 2000 to 2005, another 355,000 Chinese mainlanders immigrated to the United States, when the country saw the biggest "immigration rush" in history.

And the same thing happened in Canada and Australia, the report said.

Li Xiaoli, one of the main researchers who compiled the report, said that the immigration rushes have been stimulated by the globalization of the world economy, as well as the further opening up of China.

"Relatively higher incomes in developed countries have attracted migrants from developing countries. And as many developed countries suffer low birth rates and population aging problems, the Chinese mainland migrants fill the gap," Li said.

Li said that the mass migration has had both positive and negative effects on China.

Immigration has helped relieve the burden of employment in China. However, it has also led to a brain drain in the country as many students and professionals have gone overseas, Li said.