Migrants are a temporary solution as Singaporeans are not reproducing enough.
This was said by former prime minister Lee Kuan Yew at a National Day dinner for residents of Tanjong Pagar GRC and Tiong Bahru earlier this month.
But this situation could not persist or "this place will fold up because there will be no original citizens left to form the majority", he added.
He said the Chinese had the lowest fertility rate last year at 1.08.
If this keeps up, it means that successive generations of the largest ethnic group here will halve in size in the next 18 to 20 years.
Indians and Malays fared marginally better with fertility rates of 1.09 and 1.64, respectively, but these were also below the replacement level of 2.1.
He said: "So, our choice is simple. Either accept migrants at a rate which we can assimilate them, and make them conform to our values, and have the others on temporary work permits to help build up Singapore.
"It is a temporary solution, but not a long-term one. Long term, is a change in mindset."
As of last year, there were 1.2 million foreigners working in Singapore, 532,000 permanent residents and 3.26 million citizens.
Mr Lee ended by asking: "Do we want to replace ourselves? Or do we want to shrink and get older, and be replaced by migrants and work-permit holders? That is the simple question."
The issue is also expected to feature in Prime Minister Lee Hsien Loong's National Day Rally speech on Saturday night.
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