One interesting data point here is that recent academic research suggests air pollution in Hebei did NOT fall. nber.org/papers/w27086

Ambiguous Pollution Response to COVID-19 in China

nber.org
Dr. Abhishek Srivastava 🇮🇳 @JNUAbhishek
9 May 2020
Recent @NASAdata reveals that air pollution in north India has dropped to a 20-year low. In Delhi, the levels of harmful PM 2.5, plunged after the lockdown began — falling from 91 mg per cubic metre (mg/m3) on March 20. insightful piece by @samirsaran & @jayantsinha
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We don't have the Apple/Google data on mobility in China. So we don't have a great comparison. But at least on the air pollution data where we CAN compare, the evidence that Hubei had a tighter lockdown than eg France or Italy or Spain is pretty weak.
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Replying to @lymanstoneky
I'd expect a higher portion (than in almost anywhere outside China) of the baseline pollution in Hubei to be from electricity and heating, though.

May 9, 2020 · 6:54 AM UTC

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Replying to @davidbaron @lymanstoneky
Comparisons to Lunar New Year seem like a good reference, though.