mining theory – Why can the block production rate be as low as two per hour?

The time to produce the next block is completely unaffected by the number of unconfirmed transactions.

The time is generally expected to follow a Poisson distribution as explained in answers to a related question.

I’m no statistician so what follows may be nonsense:

A Poisson distribution with a lambda of 6 shown as a probability mass looks like this

enter image description here

So in a thousand hours I might expect to see

  • 160 hours where 6 blocks were produced
  • 45 hours where 2 blocks were produced

Either that or something odd has happened, like a couple of large mining pools going offline.

It would be interesting to gather some of these sort of stats from the blockchain record but I expect this has already been done somewhere.