Working Papers

• Fitting Dynamically Misspecified Models: An Optimal Transportation Approach, (with Jean-Jacques Forneron), December 2024.
  Abstract: This paper considers filtering, parameter estimation, and testing for potentially dynamically misspecified state-space models. When dynamics are misspecified, filtered values of state variables often do not satisfy model restrictions, making them hard to interpret, and parameter estimates may fail to characterize the dynamics of filtered variables. To address this, a sequential optimal transportation approach is used to generate a model-consistent sample by mapping observations from a flexible reduced-form to the structural conditional distribution iteratively. Filtered series from the generated sample are model-consistent. Specializing to linear processes, a closed-form Optimal Transport Filtering algorithm is derived. Minimizing the discrepancy between generated and actual observations defines an Optimal Transport Estimator. Its large sample properties are derived. A specification test determines if the model can reproduce the sample path, or if the discrepancy is statistically significant. Empirical applications to trend-cycle decomposition, DSGE models, and affine term structure models illustrate the methodology and the results.
  
  
• Targeted Testing of Dynamic Stochastic General Equilibrium Models, (with Denis Tkachenko), October 2023.
  Abstract: This paper presents targeted tests for assessing the specifications of Dynamic Stochastic General Equilibrium (DSGE) models, focusing on specific aspects such as a model’s steady state properties, dynamic properties, and properties in selected frequency bands, such as business cycle frequencies. The proposed tests can help identify variables that contribute to misspecification. The framework addresses issues of indeterminacy and weak identification. Results show that a small-scale DSGE model is rejected over the period of 1960-2007, indicating issues related to inflation dynamics and comovements between variables over business cycle frequencies, but is not rejected in subsamples when a regime change is allowed in 1979. The Smets-Wouters model is not rejected over the same period with limitations in capturing inflation dynamics. Additionally, a medium-scale model with news shocks is rejected, and issues related to hours worked are reported. The proposed methods are applicable to Gaussian (factor-augmented) Vector Autoregressions.
  
  
• Prediction Intervals for Model Averaging, (with Wendun Wang and Xiaomeng Zhang), October 2025.
  Abstract: A rich set of frequentist model averaging methods has been developed, but their applications have largely been limited to point prediction, as measuring prediction uncertainty in general settings remains an open problem. In this paper we propose prediction intervals for model averaging based on conformal inference. These intervals cover out-of-sample realizations of the outcome variable with a pre-specified probability, providing a way to assess predictive uncertainty beyond point prediction. The framework allows general model misspecification and applies to averaging across multiple models that can be nested, disjoint, overlapping, or any combination thereof, with weights that may depend on the estimation sample. We establish coverage guarantees under two sets of assumptions: exact finite-sample validity under exchangeability, relevant for cross-sectional data, and asymptotic validity under stationarity, relevant for time-series data. We first present a benchmark algorithm and then introduce a locally adaptive refinement and split-sample procedures that broaden applicability. The methods are illustrated with a cross-sectional application to real estate appraisal and a time-series application to equity premium forecasting.