> But I have read about Ricardian comparative advantage. When I looked into the assumptions behind that model, I realised they were utter nonsense.

I don't think I've ever seen anybody criticize Ricardian comparative advantage before. What assumptions did you find to be nonsense?

Personally, I've always thought the model to be too simplistic (in the real world, there are often unrelated issues that have greater effects), but never could find a systematic flaw on the model itself.