[mitthrowaway2]

I mean, you can see pretty clear evidence of sharp declines in trade and industry in all sorts of ways following the fall of Rome, such as rates of silver production tied to concentrations of atmospheric lead in Greenland ice samples. It's not just something historians made up.

[ggm]

A good point, and to the specificity of early post Roman to 1000AD feels like a valid measure. But you also see innovations in trade, arts and embellishments, cathedral building. I don't think the coining of "the dark ages" label had the luxury of gas chromatography, it was an adjective of philosophical value, figuratively applied as a value judgement.