In other words I want to be able to measure if the Roman Republic was more socialist than the French absolutist monarchy under Louis XVI.
In want to be able to measure if the Aztec Empire was more authoritarian than Communist China under Mao.
We should be able to measure how the US or EU have moved along any of these axis in the past 20 years.
Just as we cantry to measure objective data on population, industrial production, etc... we should do our best to have a meaningful yardstick in political science.