The present study describes a method for fitting Tafel parameters for multiple reactions occurring during the electrochemical reduction of CO2 over Ag catalysts. This approach combines continuum modeling and advanced data-science methods (covariance matrix adaptationevolutionary strategy (CMA-ES)) to fit the parameters appearing in the Tafel equations used to describe the kinetics of CO and H2 formation. The method developed here avoids unquantifiable uncertainty associated with the subjective demarcation between the portions of the product polarization curves associated purely with reaction kinetics and that convoluted with the effects of mass transfer. A continuum model is employed to account for mass transport and bulk-phase buffer reactions in these systems and reveals that the neglect of these phenomena leads to systematic overprediction of the Tafel slope and exchange current density obtained using traditional methods of analysis. The coupled CMA-ES continuum modeling approach is applied to 21 data sets for CO2R on Ag obtained in similar electrochemical cells to determine rate parameters for CO2R to CO and H2 with quantified uncertainty. The fitted parameter distributions were analyzed to assess agreement of the rate parameters obtained with cardinal values and those predicted theoretically. A broad distribution of Tafel parameters across all data sets is observed, but the most probable values from the generated probability distributions lie reasonably close to values predicted from microkinetic analysis and DFT calculations. The distribution of values of the transfer coefficient and the exchange current density are attributed to difference in the structure and morphology of different Ag catalysts and to the quality of the data acquired for each catalyst. While a rough correlation between these two parameters is observed, we conclude that it is unphysical and more likely due to the poor quality of the experimental CO2R data. This suggests that more rigorous standards need to be imposed on the collection of rate data. The product-specific transfer coefficient and exchange current density determined from such data could then serve as more stringent standards against which theoretical estimates of the Tafel parameters can be evaluated. Lastly, we note that our method of data analysis can easily be adapted to handle more complex reaction systems and in particular ones where both species mass transfer and bulk reactions influence the observed rates of product formation.