Before revision:  We show that the popular 'scaled PD curve ' approach is theoretically questionable and does not perform well on the test datasets. We identify two calibration approaches that are both theoretically sound and perform much better on the test datasets.
After revision:  We show that the popular 'scaled PD curve ' approach is theoretically questionable and identify an alternative calibration approach ('scaled likelihood ratio') that is both theoretically sound and perform much better on the test datasets.