Music CD units shipped in the US

American counties reported cleaner air as Americans bought fewer CDs, which sounds like a smug morality play but is more accurately a coincidence of two unrelated declines. The skies got better. The discs got worse. Whether the trade was worth it is up to you.

Both trends are long-running and unrelated. Good air quality days have generally improved across US counties thanks to Clean Air Act enforcement and tighter emissions standards, while CD sales have collapsed since their 1999 peak as digital downloads, then streaming, took over music distribution. Two curves shaped by completely different policy and technology shifts.

So the correlation is one regulation working and one technology dying, both at once. The lungs won. The jewel case did not.