Schraw, Wadkins, and Olafson in 2007 proposed three criteria for a behavior to be classified as academic procrastination: it must be counterproductive, needless, and delaying.[4] Steel reviewed all previous attempts to define procrastination and in 2007 indicated it is "to voluntarily delay an intended course of action despite expecting to be worse off for the delay.".[5] Sabini & Silver argued that postponement and irrationality are the two key features of procrastination; putting a task off is not procrastination, they argue, if there are rational reasons for doing so.