implosion = an explosion inward
You're from China. Think about it. Mass movement of citizens from the countryside into the four major cities have been like an implosion, creating very wealthy cities in a country that is still, let's be honest, shit beggar poor. If you look at Beijing, Shanghai, Guangzhou, and Shenzhen, some might believe that China was already a member of the "first world". It isn't!
Anyway, this pattern repeats itself all over the third (developing) world.