You have to click through to discover that though, and there are exceptions who have a low ratio but don't need downvotes explained to them. (I don't know if there are such users with a low ratio and low total, though.)
You can see the ration in the tool tip over the karma.
Interestingly there are users with positive ratios arbitrarily close to 50%.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.