Gathering data from Certificate Transparency logs, here's a snapshot in time of Let's Encrypt's certificate issuance rate per minute from 7-21 January 2016. On 20 January, DreamHost launched formal support for Let's Encrypt, which coincides with a rate increase.

Note: This is mostly an experimental post with embedding charts; I've more data in the queue.

Let's Encrypt Issuance Rate per Minute

https://tacticalsecret.com/issuance-rate-for-lets-encrypt/