Transparency International, world's leading NGO on this issue, has just issued its latest ranking here on which are the most and least corrupt countries and all those in between.
Two broad categories do well: Nordic and those that follow the Common Law tradition that began in England. Larger the number the more corrupt.
New Zealand is number 1 followed by Denmark and Singapore is number 3.
United States and the UK, both did worse than previous year. US dropped from 8 to 19, UK dropped from 6 to 17. I suspect the less than squeaky clean handling by DC of Wall Street in the US and the series of ministerial scandals in under-table deals in the UK were a big factor in the downgrade.
I live in 3 countries: Hong Kong ranked 12, higher than US and UK (17); Argentina (106) -- below Zambia and Tonga and Thailand (84) -- higher than Mexico (89). China is 79.
I can say with some confidence that Argentina and Thailand deserve their low ratings and that Thailand should probably in the nineties.
Generally the rankings are reasonable.