[ktizo]

You also need to factor the benefits to Canada of improved trade relations, as well as the saving in bureaucracy that you get from having a liberal immigration policy, rather than merely focusing on the direct cost or benefit of a given individual. Gut instincts of strict fairness when trying to judge people who are taking out but haven't put in yet don't always apply, especially if the cost of enforcement is higher than the cost of being more laissez-faire. And people under 25-30 pretty much can't be judged at all on that basis, for fairly obvious reasons.