in other threads it has been discussed how having more castles give a player a larger economy and justifies two smaller players attacking a larger player without it being considered "doubling" or "gang_banging".

However, I think one ought to point out that a player's economy (income) is not strictly proportional to the number of castles they have. I.e. A player with 2 castles has a smaller income than 2 allied players with one castle each.

Working on the basis of a player starting with one castle and one gold mine in his home area:
Starting income after buying all income techs and upgrading the gold mines:
Castle: 1000
Techs: 2600
Gold mine: 750
Total income: 4350.

To double his income (making it completely fair for two one castle players to gang up), a player would have to take an additionsl:
6 gold mines (4500)
1 castle , 4 or 5 gold mines (4000 or 4750)
2 castles, 3 gold mines (4250)
3 castles, 2 gold mines (4500)

Obviously, once players' kingdoms get larger, with more castles, the 2600 income from the techs have a smaller relative effect. At this point, to keep the calculations simple, an extra player in the alliance is worth about the same as a castle and 2 gold mines, on top of the castles and gold mines owned by the players in the alliance.

In campaigns where every player starts with 2 gold mines in their area, this means that an alliance of 2 players against 1 is fair if the lone player has one more castle (and attendant gold mines) than the alliance.

Please bear in mind that you can't judge a player's economy by his score as given on the ranking page, because th etribute-producing resource building aren't worth anything until the end of the game when score is calculated.

I've noticed many players completely ignore the resource buildings now until the end of game, thereby making themselves look weaker compared to players that take them as they go.