The descriptions of Persian trader and Carthage merchant ship says that they gain 25% more trade income than normal and in files it is
<GainMultiplier op="mul">1.25</GainMultiplier>
, but both template_unit_support_trader.xml and template_unit_ship_merchant.xml has
<GainMultiplier>0.75</GainMultiplier>
So normal trade income is 0.75 not 1.
Build: Jul 14, 2025 (release-a27.1, 6a576)