Empty city index

Many people are familiar with the skyscraper index. A society at peak social mood wishes to express its optimism and pride by building the world's tallest building. This usually signals a peak in social mood, which could turn even before the building finishes construction.

Another indicator worth watching may be empty cities in China. The NYTimes checks on the empty city of Ordos in:

Chinese City Has Many Buildings, but Few People

This isn't a new story, I linked to a video back in November of 2009: Real estate bubble in China?