Board Thread:Questions and Answers/@comment-74.103.122.228-20130707191237/@comment-5627887-20130708084411

It's a 50% chance per operation, rather than a fixed ratio, so it doesn't remember what it produced in order to guarantee exactly 50%, it just rolls a 50% chance each time you Pulverize a Blaze Rod. You could end up with more or less than 50% over a short series of events, but it will tend towards 50% in the long run.