The move follows Singapore's decision to adopt a recommendation of the United Nations (UN), which considers people who are away from the country for 12 months or more as having their usual residence overseas.

This group includes those studying abroad, working overseas and those who have emigrated but have not given up their citizenship.

With the revision, Singapore's resident population - made up of citizens and PRs - is 3.58 million as at end-June last year.

Including foreigners, Singapore's total population adds up to 4.59 million, below the pre-revision 4.68 million.

The change was announced yesterday by the Department of Statistics.

Calculations from its website's figures show that in the last five years, the number of Singapore residents away continuously for more than 12 months hovers between 70,000 and 90,000.

In 2003, they totalled around 80,000 and 90,000 as at end-June last year.

Demographers interviewed said the revision would prevent double-counting and help the authorities plan resource allocation better.

Calling the move 'sensible', Professor Gavin Jones from the National University of Singapore's Asia Research Institute, said: 'Obviously, somebody who is away for years is not going to be studying in the schools here or using the MRT.'

Consultant demographer G. Shantakumar said the new measure helps the UN resolve the problem of double-counting when it makes global population projections.

'A situation where two countries count one particular person as part of their individual population can be avoided,' he said.

The change does not affect the number of foreigners living here, which is around 1.01 million as at last June, a 15 per cent rise over 2006.