What is the reason for the lowest fertility rate in Shanghai?

The fertility rate in that area of Shanghai has been very low. Not now, but forever. 10 years ago, 20 years ago and 30 years ago, it was very low. You can look at the official population statistics of Shanghai. In the last 30 years, the natural growth rate of Shanghai's local population has been negative most of the time.

Then, why didn't Shanghai's local economy collapse? Can't the local old-age social security system in Shanghai work?

Because there are "immigrants" from all over the country, they keep flowing into Shanghai.

For local people in Shanghai, or for new "immigrants" who have settled in Shanghai, there is no need to worry about the old-age social security at all, and there is no need to work hard to have children. Because when they get old, a steady stream of young people from all over the country will flock to Shanghai to provide old-age services for these old people, pay fees to the local old-age insurance fund in Shanghai, and provide a steady stream of pension withdrawal sources for these old people.

News media organizations only intercept a fragment of the fact of birth in Shanghai and don't tell you more facts behind it, which is essentially selling anxiety.

So, can Shanghai play this game well for other places?

Most cities can't afford to play, because most cities don't have the unique geographical location and urban attraction like Shanghai.

Therefore, if you live in a small place, the risk that the local social security system will make ends meet in 20 or 30 years will be much higher than that in Shanghai. Or in other words, social security in some places may start to make ends meet. For a big city like Shanghai, even if there is a cliff-like decline in the birth rate in the future, it will not have much impact on them.

For the social security coordinator, the main difficulty in the future lies in whether it is a national chess game or a local unification. If it is a national chess game, social security funds will be diluted by other poor places in Shanghai, a region with a net inflow of population. If the localities are unified, the poor places will be stretched, and the rich places will have no influence.