Thanks, I tried it out and they still spawn very quickly. Maybe I wrote the line in the wrong section, this is how it looks like right now:
# Global Static Modifiers
##########################################################################
base_values = {
pirate_spawn_chance = -1000
omen_power = 1.0 #1.0 is base.
omen_chance = 0.30 #30% chance as base.
experience_decay = 0.03 #3% of current.
land_organisation = 0.2 #20% morale recovery.
naval_organisation = 0.2 #20% morale recovery.
max_friends = 2
max_rivals = 2
tribute_income_modifier = 0.5 #Base tribute modifier, 50%
badboy = -0.5 #reduce by about 0.5 each year
tyranny = -0.25 #reduce by about 0.25 each year
}