Fig. 3

Proportional hazards: a schematic illustration. Grid represent a Lexis diagram indexed by age groups (rows) and calendar periods (columns). Area and color of each bubble maps CH-RR values for two sets of rates. PH-L, constant along diagonals or cohorts (A). PH-T, constant across rows or periods (B). PH-X, constant down columns or age groups (C). PH-A, constant everywhere (D). N-PH, not constant along diagonals, rows, and columns (E)