The acoustic gradient — certified enclosed space for focused work plus open floor for collaboration — has the most direct and consistent research support for its impact on knowledge worker productivity and voluntary office attendance. Technology investments (AV, video conferencing systems) are important but are often already in place. Furniture and amenity investments improve experience but do not address the core acoustic deficit that drives home working preference. If budget requires prioritisation, acoustic infrastructure should rank first because it addresses the mechanism — the open-plan acoustic disadvantage relative to home — that is most directly limiting office ROI.