In a recent paper, (Inoue et al. 2014), we propose a methodology that can help researchers in that situation. Our idea is very simple. We propose to identify the sources of model mis-specification by introducing additional exogenous processes in the researchers’ models, beyond the structural shocks that the models already include. These additional exogenous processes, or ‘wedges’, are not structural shocks, but only additional processes that can potentially improve the fit of the model. In other words, wedges are distortions that incorporate possible model mis-specification which is not already accounted for by frictions built into the model. The idea is then to empirically identify which ‘wedges’ improve the fit of the models the most. Using this information, the researcher can identify which parts of the model are most likely to be mis-specified and can discover how the mis-specification of the model evolves over time. It also allows researchers to assess quantitatively how important the mis-specification is.