Two of the world’s most isolated and corrupt countries – Turkmenistan and Uzbekistan – have surprisingly improved their rankings in the Corruption Perceptions Index 2015, compiled by Berlin-based corruption watchdog Transparency International.

Turkmenistan, perceived as Central Asia’s most corrupt country, jumped 15 notches from the previous ranking to settle at 154th out of 168 countries, while its next-door neighbour Uzbekistan climbed 13 places to 153rd. The countries’ progress is even more impressive compared to their 2013 joint standing at 168th out of 177 countries.

Transparency International provided no reason for the countries’ big improvements in the 2015 index.

Tajikistan jumped to 136th place from last year’s 152nd. Its strongman President Emomali Rahmon is believed to have started grooming his 27-year-old son as a successor after the country’s parliament lowered the age for presidential candidates from 35 to 30.

Another country with an impressive improvement in this year’s index is Kyrgyzstan, which jumped from 136th place to 123rd, a position it shares with Kazakhstan. The region’s largest economy climbed up three places from the 2014 ranking.

Another oil-dependent nation – Azerbaijan – improved its standing by seven places and came 119th in this year’s index despite corruption scandals in the banking sector and government rattling the increasingly authoritarian President Ilham Aliyev’s administration.

The region’s best performer – Georgia – improved its position by two rankings, occupying 48th place. Armenia, on the other hand, fell by one notch to 95th place, while Mongolia jumped eight places to 72nd.