Collapse
From BurnZero
Social collapse is the resultant pattern of behavior among civilians that indicates that the normative fabric of society has been shed - when we no longer find utility in adhering to the laws and social mores that keep order.
Economic collapse is marked by the failure of existing systems - commerce, power, food/water/medicine, transportation, and security come to mind.
The collapse of a complex society is the catastrophic change to a lower level of complexity.
Collapse might occur due to: