I think the rate would vary widely from site to site, based on factors such as the site's on- and off-topic policies, popularity of the site topic, discoverability of the site (e.g. popular in Google? then expect more questions posted by new users who didn't first read the FAQ), as well as how aggressive moderators and community members are at closing questions.
Anyway – this is not complete or scientific, but for what it's worth: See the list of closed questions on Money, i.e. closed (but not deleted) questions on the site right now, in reverse chronological order. If you count the number closed just in April, there are 9. Then, look at the list of all questions on Money, also reverse order. I count 145 in April alone (almost 3 pages at 50 per page). So, 9 / 145 =~ 6.2% closed in April, and that's assuming none of the April-closed questions have been deleted yet (I haven't been on a mass-deletion spree in a little while.)
To compare, head over to Super User and look at this and this, which are similar lists to those above but for Super User. I get counts of 479 closed in April vs. 4355 total questions in April (and again, this excludes deleted questions .. which I can't see on Superuser anyway.) So, 479/4355 =~ 11%.
Based on just that one site I picked, I don't think we're closing questions too frequently. Some people think we're not closing often enough.
I'd love to see some network-wide statistics on this, though, so I'm hoping a Stack Exchange community co-ordinator / super-moderator can add to this discussion? I did find this question at the network-wide meta, but the information is stale and just for Stack Overflow itself.
Finally .. is there any one particular recent closure that concerns you? I think in the aggregate there is probably not a problem, but if you think there was something closed recently that shouldn't have been, you can shine a light on it here at meta and we can all discuss.