[ringshall]

Also,

“ roughly 10 billion words said, per person (16,000 per day * 26,280 days = ~420,480,000)“

Not sure if I completely missed something but it looks like 420m words per person.

Edit: combine these two errors and it makes sense. The 10b number is in the text but not the arithmetic.

16000 words per day * 26000 days * 11 chars per word = 4.5E9 chars per person.