Afterthought

So I looked at FRED and sure enough they have a series called Working-age Population in the United States (USAWFPNA).

Starting with yesterday's Graph #4 (renumbered) ...

Graph #1: FRED's Mystery Population as a Percent of Total U.S. Population

... I want to back out FRED's mystery population number, which I thought must be the working age population, and see if it matches this new-found series.

CIVPART is the civilian labor force relative to that mystery population number

CLF16OV/PXX
So if I divide CLF16OV by CIVPART, I get their population number:

CLF / (CLF/PXX) = CLF * (PXX/CLF) = CLF*PXX/CLF = PXX
That's the blue line on Graph #2 here:

Graph #2: Two Sources for Working Age Population

Looks same-same to me. Actually, my calc (blue) goes back farther in time than the official stat (red) so it might be useful.

Oh, and here are both versions, relative to the total U.S. population. Just so it's easy to see that both versions look like Graph #1 above and yesterday's Graph #4.

Graph #3: Working Age Population relative to Total U.S. Population (two measures)

So yeah, yesterday's Graph #4 definitely shows the working-age population as a percent of the total population. And FRED's CIVPART definitely looks at the labor force relative to the working age population -- not relative to total population.

I love all these little details.