• Journal of Labour Economics
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• v.36 no.3
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• pp.29-64
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• 2013

This paper documents the recent changes in wage density and decomposes them. Middle group is found to have shrunk, one-third of which reflects the changes in worker composition. The rest mostly reflects insufficient supply response to the rising skill demand within jobs. The pattern is more pronounced among manufacturing, large and unionized firms, and production workers.