Tropico 4: How do you level up character traits?

How are traits leveled up for the Competent, Specialist, and Expert achievements?


According to the manual

All traits start at level 1 and may be improved up to level 5 by successfully completing missions and scenarios using these traits. Improving a trait either increases a positive effect granted by the trait or decreases a negative effect 10 imposed by the trait. Trait level is saved automatically. Traits can never go down a level.

So it sounds like the key is to use each trait during a successful game.