The paper, which projects 6.9 million people by 2030, charts the country’s strategies in managing a shrinking and ageing population.
A question on Japan’s ageing society during the dialogue triggered the discussion.
Mr Lee noted how Japan refused to take in migrants and that led to the situation it is facing today.
Mr Lee said: "So I see a nation reduced to half in 20 years, and if it still continues with the same policy, reduced to a further half, and eventually, it is all over!
"To have a nation, you must have people and you must have young people to be able to drive the economy and young people buy the products — all these gadgets and fine dining — and if you don’t have that, and you refuse migrants as the Japanese do, you will just dissolve into nothingness! I think before that comes, they may change (their) policy."
A question on China’s one—child policy was also raised during the dialogue.
Mr Lee said China is headed in the wrong direction with this policy as a shrinking and ageing population will mean assets, such as property prices, will go down.
"Property prices will go down, assets will go down. There is no younger generation to put the pressure up so I think it is heading towards the wrong direction," said Mr Lee.
He added Singapore is in a similar position wit...