Task: Text Categorization
Input (English): one-percent increase in this quantity corresponds to a two-percent loss in potential GDP in the "gap version" of Okun's law. Keynes's attacks of Pigou's work about a "theory" of it led Pigou to formulate the "real balance effect" whereby a rise in this quantity leads to a drop in prices, which eventually results in this quantity becoming zero. Phelps theorized that in the long run, it can be represented by a vertical line called the NAIRU. As inflation increases, this quantity decreases, according to the Phillips Curve. Types of this phenomenon include frictional and seasonal. For 10 points, name this phenomenon that occurs when people are willing to work but can't find a job.
Output (English): Social Science