What is the largest porn distributors and producers?

[realcozy]

I'm looking to find out who the largest USA porn producers and distributors are.
The web makes this info notoriously hard to find for the paper i am writing.

If anyone has a link to a website that has this info or would be willing to share it i'd greatly appreciate it.

Also if on sharing it if you could specify if it is a distributor OR producer.

thanks