Income from trade routes is 0 when starting a saved game with trade routes established.

With trade routes established save, quit game, restart, and load saved game. Then look at the economy screen. The value for trade routes is 0. Only by switching to the foreign polocy screen and back, or by playing a turn will this field get set correctly. While the end of turn seems to include trade route income in its update, this causes some difficulty in adjusting spending rate after reloading a game.

Cheers,
Jack