"Freedom score"? Really? Some number, representing "freedom", calculated from the US point of view - it's, how should I put it... Less than impartial. Not to mention method of calculating freedom.
It doesn't seem any less contrived than standard of living scores or happiness scores. It's obviously an imperfect metric, but while it might be useless for comparing the freedom of Germany and the US, it's perfectly adequate for comparing the freedom of the US and Croatia, or of Croatia and China. For the sake of calculating the overall freedom of the world over time, as in the case of the great-grandparent's question, it works as well as anything.