Singapore's population will decline in 24 years if no immigrants come to the country during that time.
Even if its total fertility rate (TFR) -- the number of children a woman is expected to have in her lifetime – were to rise to 1.85 from the current 1.15, the decline would still unavoidable.
A decline raises the question of how workers could support an ageing population, as it is projected that 1.9 working adults will support one elderly person compared to 8.6 in 2005.
These were the findings of a demographic study on future population growth and change in Singapore released on Wednesday by the Institute of Policy Studies (IPS).
Headed by demographer Yap Mui Teng, the four-year project which started in 2007, examined 48 possible population growth scenarios by using different TFRs and migration levels, and projected the country’s total resident population level by 2050 under each scenario.
In a Today report, IPS explained, "The results of this exercise suggest that raising TFR alone will ameliorate the situation marginally. Immigration helps to reduce the dependency burden and raise the support ratio."
If TFR remains at 1.24 births per woman and there is zero net migration -- the inflow of migrants minus those who leave -- the number of citizens and permanent residents would fall to 3.03 million.
However, if 30,000 net migrants were added each year, Singapore's total resident population would increase to 4.89 million.
At 60,00 net migrants annually, it would hit 6.76 million.
Assuming zero migration but an increase in TFR to 1.85 by 2025, the total resident population would hit 3.37 million.
Explaining why the four scenarios were chosen in particular, Dr Yap said: "These in a way reflect the conditions at that time (of study)," with IPS director Janadas Devan adding that that the TFR and net migration figures chosen for the study were "realistic and reasonable".
Last Monday, former Minister Mentor Lee Kuan Yew had said during a forum with students that the IPS' "grim statistic of 60,000 migrants a year to keep our people young and economically active" was "politically indigestible".
When the government eased immigration rules in 2006 to boost population figures, many Singaporeans were disturbed by the sudden influx of foreigners as the move prefaced overcrowding problems, rising prices and increased competition for jobs and housing. It became a hot-button issue during the recent general election.
Despite monetary incentives and longer maternity leave, Singapore, which has one of the lowest TFRs in the world at 1.15, has been struggling with raising population numbers for many years.