Bar charts and separate y-axis would be cool, absolutely.
The main reason I started this thread was that I wanted a metric for the “size of government”, at least in an economic sense. North European welfare states typically spend around 50% of GDP on government services, the UK 40% the US 35% and South Korea 30%. Wikipedia List. It seems to me like a good metric, it is easily calculated in game and most people should be able to understand it intuitively. It might also be a target of a play through to reach a certain ratio, a liberal-capitalist run might aim for 20% whereas an authoritarian socialist might try to push it to 100%.
It would be weird to display spending in absolute numbers and the ratio of spending to GDP in absolute numbers but for some reason not GDP itself. The 0-1 scaled GDP value could be multiplied by the scale defined by the min_GDP and max_GDP in the game files multiplied with some time element to simulate natural population growth, inflation and so on which all increase the GDP number.
Displayed GDP = GDP sim value (0-1) * GDP scale multiplier (min_GDP / 2 + max_GDP / 2 or something) * current year