Lee Butterman created a dataset of 350 million SSL connections and then mined that for information on the state of SSL/TLS.
On the one hand, Let’s Encrypt was by far the largest registrar, accounting for almost 30 percent of the certs in Butterman’s dataset.
On the other hand, Butterman found that 3 million domains allowed RC4 or 3DES connections, and more than 4 million relied on outdated TLS including TLS 1.0 and 1.2.