I just taught may / might and the book tells the students that, "you use 'may' with things that have around a 50% chance of happening and might with a 30% chance".
Is this true?
I, for one, use might much more than may, and I dare say it's the same for lots of others. I certainly don't go around thinking about what the percentage chance of me going to the cinema is.
I may have got this wrong, sorry, might have.