Just curious.

I remember some years ago I could pick up a US $1 bill and almost
universally the printing quality would be sharp. All lines were
perfect and clean looking. Then some years back the print quality
seems to have declined. It's most noticeable on a $1 bill where it
says "FEDERAL RESERVE NOTE" on the top where now there's almost always
noticeable smudges. I'm not sure what it is. Perhaps higher-speed
presses or maybe poor control over the quantity of ink? I notice this
in larger denominations too, but those solid areas on $1 seem to be
the most noticeable.

Occasionally I come across an older note in circulation and can
immediately notice the difference.