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영어

The unemployment rate is not zero when employment is equal to potential employment. This level of unemployment is called the natural rate of unemployment, and is greater than zero partially because of transitional periods of unemployment when workers change jobs or are looking for new jobs. The unemployment rate is above the natural rate when employment is below potential employment; conversely, the unemployment rate is below the natural rate when employment is above potential employment. Adaptive expectations are based on the idea that expected future values depend upon some weighting of past values. Decision units form their expectations from past experience in accordance with some logical rules. They may, for example, assume that income has been changing and believe it will continue to shift along a related path. Rational expectations are based on the concept that anticipations are essentially the same as the relevant economic theory. It may be logical to form expectations adaptively if the economy is quite stable, but it would be foolish for economic agents to continue to act on past trends if the economy is exploding around them. Rational expectations hypothesis says that individuals will use all information available to them at a reasonable cost in forming their expectations. No obvious profitable opportunity will remian unexploited; somebody will grab it and make a profit. The pressure of competition means that the market reflects both all information and its best estimate of how that information should be used in making decisions. To date, most empirical analysis seems to find little basis to support the rational expectations model. Contrary to the theory, studies of price and output movements show and adaptive changes. While sudden spurts occur in reaction to expectations, the overall record of gradual movements appears convincing. Cyclical movements also exist. Movements of these types are hard to explain in markets which act as pictured by the theory of rational expectations.