Alliance Treasure Bonus is a game mechanic that rewards alliances that have nations which possess Treasures.
Alliances by default have a 0% Alliance Treasure Bonus. When alliance members possess treasures in their nations, the entire alliance receives a bonus to their gross income. Each treasure in the alliance increases the Alliance Treasure Bonus by 2%. Alliance applicants and nations not on the same color as the alliance do not receive this bonus.
*All Formulas Are Per Turn Unless Otherwise Noted
Alliance Treasure Bonus = sqrt(Treasures In Alliance * 4)