The list is a combination of debt-ridden welfare states, corruptocracies, and post-Soviet economies which have too much corruption and too little oil to leave the painful economic trap which Russia was in during the 1990s.
Leading the list is Hugo Chavez's corrupt-socialist state which even the high price of oil cannot cover his massive spending programs and harmful controls against market forces. Argentina, once one of the world's top ten, comes in second because the harmful legacy of national socialist syndicalism from Peron, the military juntas, and the Krichners. Greece, the current whipping boy of welfare excess, comes in at third.
Interestingly, out of control California is rated more likely to default than war ravaged Iraq where oil wealth is stolen via massive corruption.