Historically, protectionism was associated with economic theories such as mercantilism (that believed that it is beneficial to maintain a positive trade balance), and import substitution. During that time, Adam Smith famously warned against the interested sophistry of industry, seeking to gain advantage at the cost of the consumers. Virtually all modern day economists agree that protectionism is harmful in that its costs outweigh the benefits, and that it impedes economic growth. Economics Nobel prize winner and trade theorist Paul Krugman once famously stated that, \"If there were an Economist's Creed, it would surely contain the affirmations 'I understand the Principle of Comparative Advantage' and 'I advocate Free Trade'.\"