Why "probability of success" fails the people it is supposed to help
Most retirement plans still lead with a single number: the probability that a plan succeeds. It looks precise, and it photographs well in a review meeting. The problem Justin opened with is that the number answers a question clients are not actually asking. A retiree wants to know what they can spend this month, whether they can take the trip, and what happens if the market falls. A success score answers none of that. It compresses a lifetime of decisions into one figure whose meaning is genuinely hard to explain, and whose movement, up or down, rarely comes with an instruction.
Worse, the number tends to do emotional damage in both directions. A high score invites a client to spend less than they safely could, trading years of good experiences for a cushion they will never use. A falling score creates anxiety without offering an action, so the client calls worried and the advisor has nothing concrete to hand back. The session made the case that the score is not a planning tool. It is a test result, and a confusing one.
What a probability-of-success score actually measures
Justin spent time on what the number is under the hood, because the critique only lands once you see it. A Monte Carlo success rate is the share of simulated market paths in which the portfolio does not run out before the plan ends. That makes it a statement about tail risk across hundreds of hypothetical futures, not a statement about the single future the client is going to live in. Two plans with the same score can imply wildly different spending, and the same plan can swing ten or fifteen points on a normal market quarter without anything in the household actually changing. When the input that moves the headline number the most is short-term market noise, the headline number is not a steering wheel.
The retirement paycheck: a number a client can act on
The alternative Income Lab is built around is a concrete spending figure, the retirement paycheck. Rather than reporting the odds, the software derives the amount a household can spend now, given everything in the plan, and shows how that amount is expected to change over time. It is the answer to the question clients ask in plain language. Because it is a dollar figure rather than a percentage, it is something the client can hold onto, compare against their actual budget, and adjust around. And because it is recalculated as conditions change, it stays current instead of becoming a slide that ages the moment the meeting ends.
Guardrails, agreed in advance
A spending number alone is not enough, because markets move and the number has to move with them. This is where the risk-based guardrails methodology comes in. Guardrails set the adjustment rules at the start of the relationship, in writing: how far the portfolio has to drift before spending is dialed back, how far before it can be raised, and exactly how large each change is in dollars. The client sees the playbook before anything happens, so a downturn becomes a pre-agreed adjustment rather than a panicked phone call. Justin's framing is that this turns the advisor from a forecaster, who is asked to predict, into a navigator, who has already shown the client the map and the rules for changing course.
The guardrails are also where the methodology earns its credibility. The defaults are deliberate and conservative, and the rules are deterministic, so an advisor can show a client precisely what would trigger a cut and how much it would be. There is no hand-waving about probabilities. There is a specific number and a specific rule.
What it looked like live in Income Lab
The back half of the session moved into the software, where Justin built the conversation a client would actually see. He showed the spending number derived from a plan, the guardrails that bracket it, and how a change in markets flows through to a concrete, dollar-denominated adjustment rather than a moving percentage. The point of working it live, rather than on slides, was to show that the math is inspectable: an advisor can trace where the spending figure comes from and what would move it, which is exactly what is missing when a plan leads with a success score. For advisors who are new to the platform, the section below has the fastest way to get up to speed, and a walkthrough on your own client numbers is one click away.