What is R2 all about?

Which substantive meaning we can draw from the R2 statistic? The coefficient of determination is defined as the sum of squares due to the regression divided by the sum of total squares. Usually, R2 is interpreted as representing the percentage of variation in the dependent variable explained by variation in the independent variables. This definition is found by both econometrics and statistics handbooks and is widely accepted among quantitative scholars. However, this view is challenged by one of the most distinguished political science methodologists. Gary King argues that the R2 is highly misused as a measure of the influence of X on Y. This paper analyzes the R2 statistic using a non-technical approach. Our purpose is to provide an intuitive understanding of the coefficient of determination and its major shortcomings.