I’ve noticed that after the first turn in any country, you get a weird jump in approval rating.
For instance, when starting the game as France, your approval rating is around 73%. After clicking ‘next turn’ (even without changing any policies) that jumps up to 95%. The UK goes from 63% to 80%, and all of the other countries I’ve tried seem to have the same thing happen, with approval jumping up 10-20%.
Either the approval isn’t being calculated correctly when the country is first started, or after the first turn it’s being miscalculated. After the first turn, it seems much more stable, however.