Each weak state is beset by a unique set of troubles. One country's chief woe might be staggering economic decline while another's is the rapid brain drain of its best and brightest. Here are the worst performers in each of the index's 12 indicators -- and how things got so bad.
Democratic Republic of the Congo (DRC): 9.9 of 10
If you live in Congo, there's about a 50-50 chance you are under age 14. Population growth hovers at a fast-paced 3 percent annually, despite civil war, a sky-high infant mortality rate, and pervasive infectious disease.
Almost a quarter of Somalia's population, or about 2 million people, has been uprooted by conflict in recent years.
Afghanistan, Somalia: 10
Somalia's Western-backed government controls just a few blocks in Mogadishu. In Afghanistan, a thriving Taliban insurgency, the presence of international troops, and a flawed presidential election have undermined the government's legitimacy.
One out of every five Zimbabweans has fled the country over the past decade-many of them professors, doctors, engineers, lawyers, and journalists.
Niger may well be the poorest country in the world. The government lacks any ability to provide services such as education and health care; rampant illiteracy and high rates of infant mortality are the abysmal result.
DRC, Sudan: 9.5
The tiny elites in Congo and Sudan have profited enormously from resource wealth. Overwhelming majorities in both countries, meanwhile, remain desperately poor.
Sudan's south, east, and west are all in some stage of seeking autonomy from the capital in Khartoum, citing grievances that range from government neglect to active persecution.
Somalia, Sudan: 9.9
Having a president indicted for war crimes isn't a good sign, but the real measure of Sudan's woeful human rights record is its history of subduing restive regions through massive brutality.
North Korea, Somalia, Zimbabwe: 9.6
Dictators in North Korea and Zimbab- we have rigged their economies to funnel profits into regime hands -- even with their national markets in complete collapse.
In a few parts of Mogadishu, the government or African Union peacekeepers are in control. Elsewhere, it's Islamist militias, local warlords, or an assortment of rival clan factions.
Islamist and clan organizations vie for control throughout the country, and internal shake-ups have made the government spectacularly unstable.
NATO forces are not alone in trying to direct Afghanistan's future: Pakistan, India, Iran, Russia, and China are also pursuing divergent interests there.