Billable Ratio Decay

Billable Ratio Decay is the framework that separates two numbers agencies routinely conflate: utilization (hours booked against available hours) and billable ratio (hours actually invoiced against hours worked). A team can sit at 85% utilization while its billable ratio slides from 72% to 61%, because internal reviews, rework, and non-billable coordination absorb the difference. The decay is invisible on a capacity heatmap and shows up two months later as retainer margin compression. Tracking the gap between booked and invoiced hours per client gives agency operators an early warning that no scheduling view provides. The same discipline applies to AI-assisted delivery: Anthropic's Claude Haiku 5.5, priced at $0.10 per million input tokens with a 1M context window, makes automated document processing cheap enough that agencies must decide whether saved hours get rebilled or quietly absorbed into fixed-fee retainers. Tools such as Toggl, Everhour, and Hubstaff surface the invoiced side of the ratio; Float, Runn, and Resource Guru surface the booked side. Neither alone closes the loop.