Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We show that the trend of the one-sided HP filter can be asymptotically approximated by the Holt–Winters (HW) filter. The latter is an elegant, moving average representation and facilitates the computation of trends tremendously. We confirm the accuracy of this approximation empirically by comparing the one-sided HP filter with the HW filter for generating credit-to-GDP gaps. We find negligible differences, most of them concentrated at the beginning of the sample.