It is kind of difficult to tell when the highest ranking is only above 25%. My guess is that means no one is very high on whatever it is, but it could also mean that most of high ranked ones hover around 25% while only one or a very few number of countries are much above that.
I think the key to this one is what tends to max out at about 25% and also the issue of Bulgaria being one of the highest ranked ones, while some very highly developed places such as Japan, the Netherlands, Sweden, Norway, Australia and Austria all rank low compared to the rest of the First World. Essentially, what does Bulgaria have in common with the USA, Germany, Canada, France and the UK that it does not have in common with Japan, Australia, the Netherlands, Norway, Sweden and Austria?