The validity of the Kappa coefficient of chance-corrected agreement has been questioned when the prevalence of specific rating scale categories is low and agreement between raters is high. The researchers proposed the Lambda Coefficient of Rater-Mediated Agreement as an alternative to Kappa to address these concerns. Lambda corrects for chance agreement based on specific assumptions about raters and the rater-mediated assessment process including rater-specific tendencies for strict or lenient ratings. Actual ratings of teacher profiles from an inter-rater reliability exercise confirmed the shortcomings of Kappa. The rater data also demonstrated the robustness of Lambda-1, Lambda-2, Gwet's AC1, and Gwet's AC2 to the data conditions that are problematic for Kappa. All four alternative chance-corrected agreement coefficients showed less variability across the 45 raters than Kappa. However, AC-2 was undetermined for 39 of the 45 raters. Simulation data demonstrated the robustness of the Lambda Coefficient of Rater-Mediated Agreement to the data conditions that are problematic for Kappa. [This paper was presented to the virtual Annual Meeting of the National Council on Measurement in Education, June, 2021.]