Beijing traffic jams and the number 4

Excessively polluting and timewasting  heavy traffic congestion in central Beijing causes significant distress to drivers and residents alike. In a drive to identify root causes, researchers have put two and two together and come up with an improbable answer – the number ‘4‘.

“In this work we estimate the effects of traffic congestion on subjective well-being in Beijing, China. In response to heavy congestion and pollution, Beijing restricts vehicle usage on the basis of license plate numbers. On any given weekday, private vehicles with plates ending in one of two digits may not drive within the 5th Ring Road from 7 am to 8 pm. As a result each vehicle is restricted one day per week. However, superstitions regarding the number four – which is homonymous with ‘death’ in Chinese – dramatically reduce the proportion of vehicles with license plates ending in four. We thus expect, and find, large increases in traffic congestion on days on which plates ending in four are restricted.”

See: ‘Superstitions, Street Traffic, and Subjective Well-Being’ by Michael L. Anderson, Fangwen Lu, Yiran Zhang, Jun Yang, Ping Qin, NBER Working Paper No. 21551, Issued in September 2015

A full copy may be found here