Respect and mood
How the people of each nation feel about you. Happy people pay up and stay; angry ones do not.
Every nation you hold has a mood, shown as a face and a word in the War Budget panel. Content people pay their taxes and their numbers grow.
Fair taxes, victories and speaking to your people in hard times cheer them up. Heavy taxes, defeats, enemy troops on their land, unpaid troops and long silences bring them down.
Moods change slowly, drifting towards where things are heading. The panel lists the reasons, so you can see what helps and what hurts.