Employment Projections (EP) is fundamentally different from most BLS programs because it is not a survey program. Instead, EP is a model-based program that makes long-term projections of industry and occupational employment using standard and accepted economic theory and econometric techniques involving a wide variety of economic data. In the cases where multiple models are assessed, EP staff make selections based upon widely accepted econometric diagnostics and practices. In addition, there are a number of important assumptions and data limitations that are key to properly understanding and using EP data. For an in-depth discussion of these assumptions and limitations as well as the model framework, please see the Concepts and Calculation sections.