Haha, I did give some thought to the maths as I agree it sounds high. But I think your assumptions are off.

First, the assumption he made in that calculation was that most of the words are spoken during adolescence. Children do yammer on, so I find that quite believable. We probably speak less as adults, but unless you speak much more slowly than I do, one word every two seconds is extremely slow.

Think about it this way. The article you just read was over a thousand words and you read it in around five minutes. If you were reading aloud that might go up to seven or eight. 2000 words an hour isn’t actually that ambitious.