[Question] Population values for cities level up?

In CoreImprovements.xml you'll find stuff like

    <ImprovementType InternalName="CityHub1">
        <DisplayName>Village</DisplayName>
        <IsCityHub>1</IsCityHub>
        <RequiresCity>0</RequiresCity>
        <BarredTerrain>River</BarredTerrain>
        <BarredTerrain>SwampTerrain</BarredTerrain>
        <PreferredTerrain>Category:Land</PreferredTerrain>
        <PreferredTerrain>Forest</PreferredTerrain>
        <ZOCMinRadius>1</ZOCMinRadius>
        <ZOCMaxRadius>1</ZOCMaxRadius>
        <ZOCRadiusTurnsBeforeUpdate>0</ZOCRadiusTurnsBeforeUpdate>
        <BuildRadius>1</BuildRadius>
        <BuildableTiles>50</BuildableTiles>
        <CitywideDuplicateImpLimit>1</CitywideDuplicateImpLimit>
        <HideInHiergamenon>1</HideInHiergamenon>
        <LaborToBuild>0</LaborToBuild>
        <GameModifier>
            <ModType>LevelBarrier</ModType>
            <Attribute>Population</Attribute>
            <Value>50</Value>
            <CityUpgrade>CityHub2</CityUpgrade>
        </GameModifier>
        <GameModifier>
            <ModType>CityDefenseSummon</ModType>
            <Attribute>SummonUnitByClass</Attribute>
            <Value>2</Value>
            <Provides>+2 City Defender Party's</Provides>
            <UnitClass>CityDefender_Party</UnitClass>
        </GameModifier>
        <GameModifier>
            <ModType>Resource</ModType>
            <Attribute>Research</Attribute>
            <Value>1</Value>
            <PerTurn>1</PerTurn>
            <Provides>+1 Research per Season</Provides>
        </GameModifier>
        <GameModifier>
            <ModType>Resource</ModType>
            <Attribute>Gold</Attribute>
            <Value>2</Value>
            <PerTurn>1</PerTurn>
            <Provides>+2 Gildar per Season</Provides>
        </GameModifier>
        <AIName>Outpost</AIName>
        <AIData AIPersonality="AI_General">
            <AIPriority>5</AIPriority>
        </AIData>
        <UnlocksShopItem>SaltedPork</UnlocksShopItem>
        <UnlocksShopItem>Club</UnlocksShopItem>
        <UnlocksShopItem>Staff</UnlocksShopItem>
        <ArtDef>Art_CityHub1</ArtDef>
    </ImprovementType>

However the game IS hardcoded to use population for levelling up, that cannot be changed. But the values are there at least.

Wow! You are awesome! Thanks for the ino Heavenfall