A doom loop for a city or society refers to a downward/negative spiral in overall conditions. This can lead to a societal collapse if it is not stopped.
Factors that may contribute:
(1) loss of key economic drivers
(2) increase in crime
(3) decline in working population (who own property and/or pay taxes)
(4) loss of tax revenue
(5) decline in civic services
(6) poor leadership by civic leaders
(7) deterioration of infrastructure
Usually there are one or two triggering events. These may often preceded by changes in the environment that will accelerate the later decline.
An example may be:
(1) loss of a key economic driver, such as an industry
(2) there is a reduction in taxes, resulting in cut-backs to key civic services
(3) there is a surge in crime, causing people to avoid or leave the area
(4) this causes a decline in income in remaining businesses, resulting in lower tax revenues
(5) civic leaders raise taxes on population to make up for decline
(6) people leave, driving down property values and property taxes
(7) there is a further increase in crime
