Big Problems with Probability of Success in Retirement Planning
Probability of Success doesn't help retirees reach their goals - it drives them toward underspending, and feeling bad while they do it.
Last published on: August 26, 2025
Video: Big Problems with Probability of Success in Retirement Planning
Video Transcript
when you retire the main question is how
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much can I
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spend financial advisers often approach
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this question by analyzing a wide range
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of ways life could go investment returns
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could be good or bad inflation could be
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high or low or any mix of these at any
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point in time in each scenario there is
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an amount someone could spend and still
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meet all of their goals including not
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running out of money and if I asked you
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what is the most likely amount that this
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person can spend you'd say it's right in
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the middle it's the spot where half the
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scenarios would support more spending
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and half would support less for decades
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we've talked about retirement spending
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using the probability of success score
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so what's the probability of success of
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this most likely spending level 50%
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obviously but wait 50% success sounds
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terrible we usually want that score to
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be much higher maybe 100 so where on
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this graph is
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100% right here in other words in every
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single scenario the retiree could have
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spent more and still hit their
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goals 100% success is really 100% chance
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of under spending what's going on here
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the problem is that the word success
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already means something it means living
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the best life you can using your
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resources well spending time with loved
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ones diving into interests and passion
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projects doing the best you can with the
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Life Health and time you're given but
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that's not what probability of success
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means instead it thinks success means
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spend as little as possible and leave a
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large portfolio balance when you die if
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we use probability of success it will
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drive people to underspend because we
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want that score to be high just try
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convincing anyone including yourself
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that 60% success is better than 90 it's
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impossible one reason it's impossible is
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that we all know that the opposite of
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success is failure take a 75%
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probability of success it doesn't take a
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mathematician to know that that means
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one in four people are failing that's
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completely
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unacceptable but of course it's also
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wrong it's an illusion that drives us
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not toward the goal of making the best
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use of our resources to live a
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fulfilling life but toward under
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spending and reg ret and leaving a lot
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of money behind for our executive to
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handle retirement planning is really
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about balancing the risks of
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overspending and under spending we just
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saw that probability of success is
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really risk of
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underspending imagine someone has a
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retirement plan with a 90% probability
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of success then there's a market crash
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you update their plan and their
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probability of success goes down at what
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point would you start getting nervous
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we often hear answers in the 70 to 75%
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range but if the risk of UND spending
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goes from 90 to 75 these clients are
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still living well within their means
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they have no business being worried
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about running out of money and we have
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no business making them think that they
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should be worried think about it if we
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use probability of success these clients
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will think that one in four people in
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their Position will run out of money
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that's scary but in fact they're still
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in the under spending zone so what do
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you think is it time for probability of
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success to go can we do better let me
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know in the comments