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

Question

Why is it taking so long to mine a single block. Like last hour only 2 blocks have been mined. Currently been 45 min since the last block was mined.

According to blockchair

Hour Blocks
 5  *****    
 6  ******   
 7  ******   
 8  *****   
 9  ******** 
10  ***      
11  ****     
12  **       
13  **       

What could make 45 minutes go by without a single block being mined and having so many unconfirmed transactions still?

Answer 1

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

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.