So it means more and more elders will be left unattended. In a Beijing community, 20 households have found a special way to look out for elderly residents, especially those who live alone.

Blinds carry a secrete code that's only shared between 79-year-old Sun Yufen and her neighbor.

"We keep an eye on each other's windows regularly. If the blinds remain closed down, it signals that something's gone wrong, because we might get too sick to even make a phone call. We'll come to knock on each other's doors. If nobody responds, we'll then get our neighborhood committee," said Sun Yufen.

Sun and her husband still manage to do some light housework. Their children can't visit them all the time.  But 80-year-old Su Guiru has been living on her own since her husband passed away several years ago.

"We work in pairs. She keeps me on her mind and comes to check on me often. And I do the same. There's a bond between us. It gives me peace of mind knowing somebody cares about me," said Su Guiru.

The idea of a curtain pact originated from two families who supported each other for more than two decades in a neighboring community. When the idea was introduced to this neighborhood by social workers, residents worked out their own curtain codes.

Mrs. Han, 72, has suffered from a leg illness for a long time. Whenever she puts her blinds down half way, her paired neighbor Mr. Liu will help by bringing groceries to her apartment.    

"Ten pairs of families in this community have made their curtain pact, but they are only a very small fraction of the seniors who live without carers. Social workers have told me that this community has about 2,000 seniors. One-fifth of them are what many call "empty-nest" seniors.

"The curtain pact is only a formality. What we hope to achieve is establishing a platform for volunteers and seniors to communicate with and help each other. We hope to get more residents to take part," said Xu Yanling, director of Jiangongnanli Neighborhood Committee.

Xu says they are hoping to double the number of families who join the curtain pact in the coming year.