The similarities between Poland and Argentina were striking. By the time the Soviet Union collapsed, the two countries were beacons of reform in their regions. Each had a largely Roman Catholic population of about 36 million. Both were introducing free-market reforms. And after decades of authoritarian rule, both were establishing democracies. Argentina seemed the better bet. Its democracy was farther along and it had already begun a number of privatization programs. The Poles started out with neither. Then, in 2001, Argentina was hit by a severe economic crisis which it has yet to recover from. Poland, meanwhile, has gone on to experience strong economic growth. Wharton management professor Gerald McDermott , whose research focuses on international institutions, began to hear a joke circulating in Latin America several years ago: If you want your country to get rich, join the European Union. McDermott began to question whether there was more to that idea than a joke.…