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Table 1 Definitions of Numerators and Denominators

From: Calculating incidence rates and prevalence proportions: not as simple as it seems

  Numerator Denominator
Incidence rate
 Incidence rate: person-years Sum of all new episodes of illness in 2012 Person-years
 Incidence rate: person-years at-risk Sum of all new episodes of illness in 2012 Person-years at-risk
 Incidence rate: midterm population Sum of all new episodes of illness in 2012 Midterm population
Prevalence proportion
 Point-prevalence proportion Episodes on December 31th Population on December 31th
 1 year period prevalence proportion Episodes in 2012 Person-years
 Contact prevalence proportion Number of persons with ≥1 contact in 2012 Person-years