[posedge]

Are the tweets filtered for the event in any way, or is it just a random collection from all of twitter on that day?

[CodesInChaos]

Looks like it's based on search queries:

pandemic 5847

lockdown 5847

testing 5847

vaccine 5847

covid 5843

stock market 5843

jobs 5843

president 5842

mask 5840

travel 5839

spread 5837

economy 5836

quarantine 5836

unemployment 3045

coronavirus 2822

death rates 495