On the colonization map every independent province has values displayed enumerating the probable chance of success for colonizing and establishing trading posts in the province. I know that the probability of success can be improved by occupying the province with an army or a conquistador, and that once a trading post is established the likelihood for subsequent attempts at expanding the post improves. The same is true for colonization, once a colony is established attempts to send more settlers becomes increasingly more likely to succeed. Are there other ways to increase the base probability of successsfully establishing colonies or trading posts?