text: Following the approach of the Section 812 Prospective Report , we estimated the percentage change in the prevalence rate for chronic bronchitis using the estimated coefficient from Schwartz 's study in a C-R function , and then applied this percentage change to a baseline incidence rate obtained from another source .
  
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  Following the approach of the report , we guessed that the percentage change in the prevalence rate for chronic bronchitis using the coefficient from the study .