I think free trade has benefited mankind hugely and is largely responsible for lifting China out of poverty. However, I don&#x27;t find the standard model of comparative advantage to be a convincing argument in favour of free trade.<p>The problem is that the basic model is heavily oversimplified, and more complex models get very complex very quickly. With a model, it&#x27;s hard to be sure you&#x27;ve captured all the effects and calibrated it correctly (especially in a world with changing demographics and changing technology).<p>I think most intelligent people hear the basic idea, and then come up with criticisms like the following:<p>1&#x2F; It appears to assume that comparative advantage is fixed. But couldn&#x27;t a country deliberately specialise in something it&#x27;s not innately good at, thus retraining its workers and eventually shifting its comparative advantage over time?<p>2&#x2F; All the textbook examples concentrate on manufacturing. It&#x27;s not a giant leap to see the same effect in services, but I don&#x27;t think it&#x27;s completely clear-cut either.<p>3&#x2F; It assumes labour is immobile. Otherwise why wouldn&#x27;t the specialist weavers from England move to France and the specialist masons from France move to England?<p>4&#x2F; How can a country know what its comparative advantages are? Comparative advantage is not observable in the real world, so producers have to resort to guesswork. How can we know they guess correctly?<p>Now if you ditch some of the basic assumptions it&#x27;s not at all clear how the conclusions change. So I think it&#x27;s perfectly reasonable for laymen not to be convinced by the basic model.