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The economist Robin Hahnel has argued that free markets are in fact systematically inefficient because externalities are pervasive and because real-world markets are rarely truly competitive or in equilibrium .
 Robin Hahnel
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Robin Hahnel