I was at a bee conference at Penn State a couple of years ago and an ARS scientist gave a paper that addressed this issue. If memory serves me, in the sample they examined, the supersedure rate was well over 50% for new introduced queens within the first 6 months of installment. I don't know of any studies but I believe Iddee is correct in that the queens reared by a hive are longer lasting. I still requeen to continually improve the genetics in my hives because those young larvae used as supersedure queens came from the queen I purchased. Then, there's the other half that were accepted over the long haul.