The PDI is based on how much the citizens of a country defer to those in power. Americans, having a low PDI, are accustomed to speaking frankly to superiors as the occasion demands. A study of the airline industry revealed that South Korea has the second highest PDI of any country in the world (e.g., are much less likely to speak frankly to superiors). (Blanding, Michael. The Brain in the World – A Burgeoning Science Explores the Deep Imprint of Culture.)