My team is carrying out incidence estimation in ATLAS and a question has come up regarding a discrepancy with the person-years for the incidence estimates. The person-time for the stratified estimates do not sum perfectly to the person-time for the overall incidence, and these numbers are far enough off that rounding cannot explain the discrepancies. For example, the overall person-years for one incidence was 516 years; whereas, for males it was 310 years and 216 years for females (total = 526 years). Is there an explanation for this difference? We see this across many of our incidence analyses.
Thank you very much for your help!