Playing right now, and the National Epic +15% bonus is wonky. Not adding up right at all -- the +15% from Rationalism is fine, though. The food added per turn is in line with what the (incorrect) amount is listed. For example -- at -5 food, after the +15% National Epic bonus, I was at -4 food. At +14 food, it put me at +14.3. At +20 food, at +20.89. On the other hand, after taking Rationalism, I'm clearly getting the +15% bonus -- note, growth is NOT according to total food, it is, as I thought, food *surplus*. So growth is not as good as holding food over, if when you grow, you aren't adding at least 3 food. Also, strategery-wise, it is clear that just plowing through Tradition is a bad idea if you are going something OCC'ish. Tradition --> Aesthetics --> Tradition is far wiser.