yearly_0001_set_random_weighted_skill_effect

yearly_0001_set_random_weighted_skill_effect = {
	set_variable = {
		name = yearly_0001_skill
		value = flag:diplomacy
	}
	random_list = {
		20 = {
			#Must be better at the skill we pick than our liege.
			trigger = {
				$MENTEE$.diplomacy < $MENTOR$.diplomacy
			}

			$MENTEE$ = {
				set_variable = {
					name = yearly_0001_skill
					value = flag:diplomacy
				}
			}	
		}
		20 = {
			#Must be better at the skill we pick than our liege.
			trigger = {
				$MENTEE$.martial < $MENTOR$.martial
			}

			$MENTEE$ = {
				set_variable = {
					name = yearly_0001_skill
					value = flag:martial
				}
			}
		}
		20 = {
			#Must be better at the skill we pick than our liege.
			trigger = {
				$MENTEE$.stewardship < $MENTOR$.stewardship
			}

			$MENTEE$ = {
				set_variable = {
					name = yearly_0001_skill
					value = flag:stewardship
				}
			}
		}
		20 = {
			#Must be better at the skill we pick than our liege.
			trigger = {
				$MENTEE$.intrigue < $MENTOR$.intrigue
			}

			$MENTEE$ = {
				set_variable = {
					name = yearly_0001_skill
					value = flag:intrigue
				}
			}
		}
		20 = {
			#
			trigger = {
				$MENTEE$.learning < $MENTOR$.learning
			}

			$MENTEE$ = {
				set_variable = {
					name = yearly_0001_skill
					value = flag:learning
				}
			}
		}
	}
}

As written in game/common/scripted_effects/00_yearly_event_effects.txt.