In the Sanska era, cities in the world experienced a rapid decline in population, as more and more people began to move to the rural parts of the world to escape easily transmitted diseases, which were rampant at the time. Also people began to find negative effects of a city, and also the natural disasters occurring at the time. The sharpest decline experienced was that of Beijing in the People's Republic of Northern China, where ten million residents escaped to the countryside areas.
|City Name||Country||Decline Experienced||Cause||Ranking of Most Sig. Decline||Notes|
|Beijing||PRN China||9.4million to 10.5million||Mers outbreak in neighbouring cities||1|
|Shanghai||Chinese Rep.||9.5million to 10.3million||Mers outbreak in neighbouring cities||2|
|New York City||United States||9.4 million to 9.5 million||Azores megatsunami||3|
|Seoul||R. of Korea||9.1 million to 9.4 million||Mers outbreak||4|
|Los Angeles||United States||9.0 to 9.3 million||San Andreas fault earthquake and influenza.|
|Pyongyang||PR of. Korea||7.2 million to 7.9 million||Mers outbreak|