The result is a bias toward providing concentrated benefits and ignoring much larger, but dispersed costs. Therefore, it is often the case that the smaller the number of people benefiting from a policy, the more powerful their political influence in its favor. For that reason, government is a constant threat to the social cooperation that comes from free-market activity. The costs of trade restrictions are more difficult to identify than indicated above. Consider restrictions on steel imports.
Few people buy steel directly.
Rather they pay for it indirectly when they buy products made from steel. Also, when an import restriction increases steel prices, employment opportunities are reduced in industries relying on steel as an input. Those who don't get jobs because of a trade restriction will seldom know the reason. If such costs were revealed, rather than concealed, by the political process, we would never reduce our prosperity with trade restrictions. The advantage we all receive from free trade is that it forces industries to consider the full opportunity costs of their productive activity.