When the European Community Was Originally Formed, It Was Determined

When the European Community was originally formed, it was determined that the common external tariff on outside world products should be equal to the average of the preunion tariffs of partner countries on the outside world. This rule was adopted so that there would not be a net increase in protection against the outside world. Thus some partners raised tariffs on some products and lowered them on others. See if you can show how this "averaging" rule would complicate the process of making welfare judgments about the likely effects of the original formation of the EC on the member countries.