A General Class of Score-Driven Smoothers
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Motivated by the observation that score-driven models can be viewed as approximate filters, we introduce a new class of simple approximate smoothers for nonlinear non-Gaussian state-space models that are named "score-driven smoothers" (SDS). The newly proposed SDS improves on standard score-driven filtered estimates as it is able to use all available observations when reconstructing time-varying parameters. In contrast to complex and computationally demanding simulation-based methods, the SDS has similar structure to Kalman backward smoothing recursions but uses the score of the non-Gaussian observation density. Through an extensive Monte Carlo study, we provide evidence that the performance of the approximation is very close (with average differences lower than 2.5 simulation-based techniques, while at the same time requiring significantly lower computational burden.
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