Capacity Is the New Margin Lever: Why Resource Planning Decides Agency Profitability

Agencies now sell AI-augmented delivery, but the scarce input is no longer tooling, it is senior human hours that can be pointed at the right client work. Resource planning is the discipline that converts a fixed headcount into variable margin: utilization above roughly 75% without burnout protection turns billable revenue into rework and attrition, while underbooking quietly subsidizes every retainer. The agencies winning 2026 pitches are the ones that can show a client a defensible staffing model, not just a scope document.