Author Contributions:Study concept and design: Lacy, Hogan, Rajkumar, and Schroeter. Acquisition of data: Lacy, Hogan, Gertz, Dispenzieri, Hayman, and Schroeter. Analysis and interpretation of data: Lacy, Hogan, Dispenzieri, Kumar, Litzow, and Schroeter. Drafting of the manuscript: Lacy, Hogan, and Schroeter. Critical revision of the manuscript for important intellectual content: Lacy, Hogan, Gertz, Dispenzieri, Rajkumar, Hayman, Kumar, Litzow, and Schroeter. Statistical analysis: Rajkumar. Administrative, technical, and material support: Lacy, Hogan, Gertz, Dispenzieri, Hayman, and Schroeter. Study supervision: Schroeter.