Another guess

So here's another guess at a possible future ...

In the next two to four years, the world economy more or less claws its way back to not shrinking. The US grumbles, but the rest of the world has more trouble.

After a while (e.g. 2-5 years), either China or Pakistan goes unstable. There is widespread civil unrest in those countries. At some point, Pakistan and India go to war.

Then the middle east and north africa go unstable. This causes oil production, which was dropping already, to drop quite a lot.

That in turn, affects food production, which was barely keeping up with population growth, to drop. Asia and Africa see local fighting, of the Somali pirates and Darfur crisis variety in much larger amounts.

The lack of food and civil disturbance drives people into environments, like refugee camps, in which many people are crowded together with minimal sanitation and food. These spawn epidemic diseases, which spread beyond the camps to the cities.

Some people react by forming into militias to take over their neighbors resources. Existing infrastructure (e.g. roads, bridges, farms, oil wells) is destroyed. This reduces the effective carrying capacity of the affected regions.

World population drops, due to starvation and disease, mostly, with some warfare thrown in.