What would could have caused a major ecconomic crisis?

What event or series events could cause a society to plunge into ecconomic despair. Where even highly skilled people are caught in a slum. What would entertainment be like? Would there be others in higher power that hold more money or rights? Could civil rights not have been recognised to cause this?
 
Well a Western nation, any period - possibly modern... what if China was a super power for example or had colonised a lot of the western world, taking its gold and gems etc..?
 
Nation: America, Britain
Condition: Survelience is increased, the panotpican exists as a prison system, crime on the increase, unemployment of highly skilled workers
Super-powers: China, India


How could this and when could the events leading up to this occur?
 
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