Raymond Williams’ theory that values are intrinsic to variable definitions of categories guides our inquiry into how shifts in the category of efficiency can help us to understand the category of work. Who deploys efficiency to describe which practices and how do claims of efficiency become central to power struggles? What is the relationship between efficiency and labor and between efficiency and corporations seeking higher productivity? This chapter takes a historical and comparative approach to analyzing the complex socio-historical construct of efficiency. During the twentieth century, the category of efficiency was contested by labor and capital even if at times they sought mutual accommodation. Struggles over efficiency, however, played out not only in factories but also in interpretations published in journals meant for public consumption. We first trace definitions of efficiency using traditional historiographical methods and then compare two very different textual sources, the International Labour Review (ILR) and the Harvard Business Review (HBR) published respectively by the International Labour Organization (ILO) and the Harvard Business School. Applying a topic modeling approach (latent Dirichlet allocation, or LDA), this study employs natural language processing tools (NLP) to find patterns in large textual corpora in conjunction with classic historiographic methods.