Veenhoven is also interested in the inequality of happiness ratings within countries. In other words, how similar are the happiness ratings of various individuals within any given country? He constructed a measure called Inequality-Adjusted Happiness, which was based on the standard deviation of happiness ratings. The standard deviation is a statistical measure that reflects how much individual cases vary from the average. According to his calculations, the top five countries with both the highest and most equal happiness ratings were Malta, Denmark, Switzerland, Iceland, and the Netherlands. The middle five were the United States, the Philippines, Iran, South Korea, and India. The bottom five were Armenia, Ukraine, Moldova, Zimbabwe, and Tanzania.