Table 1.
Definitions of Numerators and Denominators
| 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 |