The ranking of countries on this graph would be affected by both the level of participation and the level of achievement as it is for the awarding of the Qualifications. This got me wondering what might have contributed to the obvious educational advantages that females in some nations seem to enjoy.
I compared this graph with the order in which countries adopted female suffrage.
Out of the top 10 countries in this graph 8 were also amongst the first 10 countries to give females the right to vote. The length of time between these two occurances is around 100 years so it would be difficult to draw a direct link.
One could suggest that these countries still have a very progressive outlook on social issues such as equality and education.
An even more obscure link could be that females in these countries got a "head-start" on females of other countries by getting the vote so many years ago.