Lexis diagrams (cont.)

Unfortunately, translating period data to cohort data in this way does not give us a real cohort in the strictest sense.

It is easiest to understand why this is by looking at the same data depicted on a Lexis diagram.

The black boxes represent the age-specific data highlighted in pink on the previous table. Theoretically they should represent a cohort. However if we add in true birth cohorts, we can see how they do not directly correspond.

Interaction Click the arrows to see the birth cohorts which fall within these boxes.

Person-years of exposure to risk
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