If I want to use a repository, my first step is to either download a released binary or clone the repository. Forking is much further down the line for me, when I've used the code, encountered a problem, fixed it, and decided to polish the fix up to make a PR. I star something when I either have used it and like it, or when I think I want to use it in the future and want to bookmark it (though the former more often than the latter). I have given out about 50% more stars than I've forked, and have probably cloned an order of magnitude more than I've forked or starred.
Of course not everyone is the same, but I'd be surprised if overall clones were less than an order of magnitude more than forks or stars, and find two or even three orders of magnitude believable depending on the target group of the repo.
Exactly. I would add that the number of clones (not forks) and file/page views is viewable only by the owner of the repo, so we can only guess. (If you own a github repo, you can see the most recent number of clones and page views by clicking on insight -> traffic.)
My estimate of "one to two orders of magnitude" is based on anecdotal evidence. I edited my comment to reflect as much.
Of course not everyone is the same, but I'd be surprised if overall clones were less than an order of magnitude more than forks or stars, and find two or even three orders of magnitude believable depending on the target group of the repo.