SSL Certificates are used to encrypt data between 2 points. For example your web browser and a web server. Most banks, online stores and other websites that deal with sensitive information use SSL encryption to protect the data you are sending over the internet.
Normally webmasters need to buy an SSL certificate from a SSL certificate vendor, (with the exception of Let's Encrypt).
To generate these statistics we have connected to all the websites in our database and extracted the SSL Issuer from the certificate data. Websites that do not have an SSL certificate or do not force SSL on their websites are excludded.