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But demographics measure age of population from birth to death.
And IBM measures only workforce from 21 to retirement.
Are those measures of median age comparable?


Mikhail: In both cases, each person ages one year per year. If the work force did not change, then the median age should go up by one year per year, no?


Only if nobody retires. When an employee retires and he is replaced by a new employee, his (presumably) high age is substituted by a zero one.
But I admit to know nothing about job market in US. Or am I missing something other?


Antonio: We can work this out in the comments. That substitution would barely change the median age. If a big chunk of the older workers left, and were replaced by younger workers, the median age might even decline. But that may be proof of age discrimination - as presumably older workers are in more senior positions and so should not be replacable by young workers.

The other factor is whether the total size of the workforce increased or decreased, and which jobs have been added or removed (age interacts with experience and job requirements).

The key point is that it is not obvious to me that age structure being invariant conveys much information (by contrast, gender mix being invariant is more informative).

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