The Sketch uses geometric compounding. Each scenario runs a band of three growth paths — conservative, baseline, and upside — which form your Floor, middle projection, and Ceiling. Optimistic: 2.0–4.0–6.5% real (markets performing well above average). Historical: 1.5–3.5–5.5% real (anchored to long-run averages). Stress: 0.5–1.5–3.5% real (compressed returns, heavy downside guardrails). Inflation: Real strips inflation out — all values in today's dollars. Nominal adds 3.0%/yr inflation, showing the raw future dollar amounts.

Your Floor and Ceiling each use a withdrawal rate tuned to the question they answer: the Floor uses a reduced rate for resilience under a conservative path, the Ceiling uses an elevated rate for capacity under an upside path. Your Datum is different — it always shows the capital required to sustain your chosen spending at the canonical 4% rule, regardless of where it sits in the Shape. That way the three boundaries answer three honest questions: "what could break" (Floor), "what could stretch" (Ceiling), and "what would my spending cost as capital" (Datum).