The great folks over at Mailchimp publish aggregate stats from their customers. This is a useful set of data for senders who want to see how other mailers or ESPs are doing.
One set of stats is the data from
234 million emails delivered by our system (where campaign tracking was activated, and where users actually reported their company size) and calculated average open rates, average click rates, average soft bounces, average hard bounces, and average abuse complaint rate by company size.
Good stuff, Mailchimp.