Annals of Economic and Social Measurement, Volume 5, number 2
    Published Date 
  
  
    Copyright 1976
  
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                Sanford V. Berg. 2019. Annals of Economic and Social Measurement, Volume 5, number 2. NBER. https://www.nber.org/books-and-chapters/annals-economic-and-social-measurement-volume-5-number-2.