China is using mobile phone signals to map its ghost cities

Some of the ghost cities identified by Baidu researchers. Image: Baidu.

You'd think it'd be relatively hard to mislay a city. Cities are, by definition, very large things: losing one sounds like it should be much more challenging than losing, say, your car keys, or even your entire car. 

But in China, there are entire cities which go relatively unaccounted for. This is the result of a combination of fast development, low regulation, and the fact that many Chinese cities are still practically empty. 

This is why it's pretty hard to get a figure for just how many "ghost cities" – cities that exist, but lack residents – there are in China. Most of these cities have some residents, making "ghost" a relative, and pretty hard to define, term. 

So Baidu (basically, China's Google) decided to work it out. The researchers behind a new study, "Ghost Cities: Analysis Based on Positioning Data in China", used location data from users' phones, plus mapping and building location data, to find areas with high volume of buildings, but a low density of people. The researchers also tried to discount vacant areas that were empty because of tourism: apartments only filled in high tourism season, for example. 

Here are some areas of vacant housing they found in nine different cities: 

Overall, the researchers say they found over 50 ghost cities, though they only revealed around 20 in the report, so as not to adversely effect the real estate market in the rest. (No comment.) 


As the researchers admit in their conclusion, this isn't a conclusive study: it relies, first and foremost, on the idea that "Baidu users" are a good proxy for "people", and that areas with no Baidu activity are empty. Yet as they note, arrogantly and probably accurately:

With the ubiquity of smart mobile phones, Baidu users occupy the most proportion of the whole population. 

This does seem to be one of the more accurate surveys of China's ghost cities produced so far, even if the researchers won't release all the details. That could mean greater accountability for the development firms who toss up concrete blocks and then fail to fill them. 

 
 
 
 

Podcast: It’s Always Sunny...

The Liberty Bell. Image: Getty.

Once upon a time, Philadelphia was the state capital of Pennsylvania. It was also briefly the capital of the early United States, the country’s financial capital, and its largest city.

Today, it’s none of those things – even the state capital long since moved to Harrisburg, which I bet you’ve never even heard of. This no doubt has an impact on the psyche of a city that was once the most important in the US, but now struggles to make the top five.

To talk about Philly, past, present and future, I’m joined by Nathaniel Popkin. He, along with Joseph E. B. Elliott and Peter Woodall, is the author of the beautifully illustrated book, “Philadelphia: Finding the Hidden City” – and had all sorts of fascinating insights into one of the United States’ more historic but lesser known cities.

Incidentally, this week, I’m recording the first ever live Skylines at the New Local Government Network conference in London’s Guildhall. If all goes to plan – If – you should be able to hear that next week. Wish us luck.

The episode itself is below. You can subscribe to the podcast on AcastiTunes, or RSS. Enjoy.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason. 

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