How are a Plan's Guardrails and Spending Capacity Calculated?

Learn how Income Lab calculates a plan's guardrails and spending capacity.

Written by Mawukle Yebuah

Last published at: January 28th, 2026

 

At its core, a retirement income plan made and managed in Income Lab answers the following questions:

  1. How much can I spend?
  2. What change in my account balance would make an adjustment up or down a good idea?
  3. What could those adjustments look like, in dollar terms?

 

You will find the answers to these questions on the main plan dashboard. The Spending Capacity card answers question 1. The bottom green and red sections, referred to as the Guardrails, answer questions 2 and 3.

Video: How Spending Capacity and Guardrail Numbers are Calculated

Video Transcript: How Spending Capacity and Guardrail Numbers are Calculated

one of the key questions you can answer

0:02

with income lab is given my resources

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and other things in my my plan how much

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can I spend and you get the answer to

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that in the retirement paycheck or

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spending capacity of a plan and you also

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get information on when you would change

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either up or down the amount of spending

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those are the guard rails we often get

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questions okay that's that's great but

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how are you arriving at that number so

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I'm going to go over that here and also

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talk about how you can talk about that

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with clients so how do we answer that

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question how much can I spend well in

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any kind of deep analysis of retirement

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spending what we're really asking is

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given the resources of the plan the

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length of a plan um certain amounts of

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planned spending given the assumptions

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about how um returns could work

0:55

inflation can work and so on what can I

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spend and in figuring that out we look

1:00

at a huge range of how the future could

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work so you could have high returns low

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returns High inflation low inflation and

1:08

so on and in each way that the future

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could work there is an amount that you

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could spend um and exactly hit your your

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goals and if we stack those all up they

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might look something like this so we'd

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have some scenarios where you'd have to

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spend very little to get through that

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world in some scenarios you could spend

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a ton and still get through that world

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but in most of them you're kind of here

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in the middle and if I asked you what's

1:32

the most likely amount that you can

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spend the the best answer to that

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question what can I spend you would say

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it's this one the one right in the

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middle that's the one where half the

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time you could have spent more half the

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time you could have spent less so it's

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the the best

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guess another way to think about this is

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that that best guess is the dividing

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point between the chances that you're

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overspending and the chances that you're

1:59

under spending to the left of that

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dividing line is the under spending Zone

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it's the the spending capacity or the

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retirement paycheck that is living

2:10

within your means anything to the right

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is in the overspending zone it's where

2:15

you're living above your

2:17

means so I'd encourage you to adopt this

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way of thinking about finding a spending

2:23

capacity or retirement paycheck you're

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trying to balance the risk of

2:27

overspending of course that's the one

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people worry about the most we don't

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want to over tax our resources but

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you're trying to balance that risk the

2:35

risk of overspending with the risk of

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underspending typically that means

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you're going to find an initial spending

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capacity or retirement paycheck that's

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within the under spending Zone hard far

2:47

within it will depend on the how much

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the spending matches up with the what

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the client wants to spend so if they

2:56

want to spend a ton you may have to um

2:59

creep up a little bit in the under

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spending Zone and take on a little bit

3:02

more risk you're still in the under

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spending Zone you're still living within

3:06

their means uh or if they if their

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resources support a lot of spending and

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they really don't need it you can go

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further back in the under spending zone

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so you might be able to choose a risk of

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under spending of around 90% only a 10%

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chance of overspending and that allows

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things to get worse the risk of

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overspending to go up the risk of

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underspending to go down and they're

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still in the UND spending Zone you can

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find this overspending under spending

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Concept in a plan on the main dashboard

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so here we have a plan with you know two

3:39

and 3/4 million in portfolio plus Social

3:43

Security and lots of other resources and

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ALT together we're at an $188,600 a

3:48

month retirement paycheck and you might

3:50

wonder where that comes from you can

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just open these settings on the side go

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down to income setting and you'll see

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that here we're targeting an estimated

3:59

20% risk of overspending and at 80% risk

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of underspending your risk of

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underspending is well above 50% so

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you're well within the underspending

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zone and so this is kind of a moderate

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setting you can see that you can be on

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just these default income settings you

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can be as high as a 99% risk of

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underspending so only a 1% risk of

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overspending extremely conservative but

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that that works for some people or on

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the default you can go as high as a 60%

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risk of UND spending

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um sorry as low has a 60% risk of under

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spending and a 40% risk of overspending

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so you're getting more aggressive the

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other place you can see the effect of

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that is in the guard rails so here again

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if I ramp up my risk of

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overspending and I can spend more um

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that also means I'll have less space

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between um now and having to potentially

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take a pay cut and more space between

4:58

now and potentially taking pay raise

5:00

then for example if I was way on the

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other side now I have I could go down

5:06

29% before taking a pay cut and have a

5:09

very small um difference before I take a

5:12

pay raise so that's just the trade-off

5:14

between my current risk of overspending

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and underspending and where these guard

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rails live so that's a an explanation of

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where the retirement paycheck or

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spending capacity comes from um where

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ENT

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helping you find a place where you have

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the right mix of overspending and under

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spending risk and for those of you who

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have done the uh master classes in the

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past you may remember that when we say

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risk of underspending that is equivalent

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to probability of success and we've

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we've spent a lot of time talking about

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why probability success is the wrong uh

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measure for retirement plans um but if

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you're wondering kind of what we're

5:56

talking about that's a you can do that

5:58

that translation in your head it's much

6:00

better thought of as uh balancing risk

6:03

of overspending and risk of

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underspending so if a client is asking

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well how did you get that number one way

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to address that is to say our role is to

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provide you with a retirement spending

6:15

level that is living within your means

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uh and that means not overspending your

6:21

resources but we also don't want you to

6:22

be under spending and take on a high

6:25

risk of regret where someday in the

6:27

future you look back and say oh I wish I

6:29

had bet more so we're trying to balance

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those two things and that's what this is

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this we believe is uh within your means

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but it's not massively underspending

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your

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resources the next question people often

6:42

have is okay great but why are these

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guard rails what they are think about it

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this way an upper guard rail is telling

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you when it's time to spend more or at

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least when you should feel comfortable

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spending more when would that happen it

6:57

would happen when your risk of under

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spending is too high it's just become

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incredibly high and so in all of our

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defaults um this guardrail is hit

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whenever your risk of underspending hits

7:11

100% what about the lower guardrail

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that's the one people tend to care more

7:15

about when would you take a pay cut it

7:17

would be when your risk of overspending

7:20

is too high and it's probably not going

7:22

to be you know a 51% chance of

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overspending you need to be really sure

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someone is overspending before before

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you recommend a pay cut people don't

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like to take pay cuts so on all our Vol

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defaults this would be hit whenever your

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risk of overspending is 75% or more you

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can see

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these levels in the advanced plan

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settings if you go to income

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settings I'll click customize just so

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that you can see them and you can see

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okay our upper guard rail is when a risk

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of

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under spending is 100% our lower guard

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rail is when my risk of overspending is

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75% you actually can customize these and

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change where you want them to be you

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know for example I can change my lower

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guard rail to be at a risk of uh under

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spending risk of 90% instead of

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100% so to summarize the retirement

8:22

paycheck or spending capacity and the

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guard rails all come from measuring the

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risks of overspending or under spending

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for a particular plan and these

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are specific customized levels for the

8:36

particular plan you're looking at so

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there are no rules of thumb built in

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here they're using the actual plan with

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its particular sequence of return risk

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sequence of inflation Wiis risk

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mortality risk longevity risk and coming

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up with a retirement paycheck that is

8:52

living within someone's means but is

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balancing the risk of overspending with

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the risk of regret and the guard rails

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are the levels at which your risk of

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regret is getting too high in the case

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of the upper guard rail and the risk of

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overspending is getting too high in the

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case of the lower guard rail and because

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we're constantly measuring these risks

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the guard rails will actually change

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over time um in fact if you saw a plan

9:19

where the guard rails are not changing

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that would be that would be strange uh

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just think about you know if these are

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the guard rails today in 10 years they

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better be different uh at the very least

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because these people will be 10 years

9:31

older so that's kind of the the the

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magic of using overspending and

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underspending risk to to manage the

9:40

retirement paycheck and the guard rails

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is that you're always taking into

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account whatever the risks are on the

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ground at that point um so hopefully

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that helps explain both um for advisers

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with the analytics are behind it but

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also giving you some language to use

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with clients to explain where these

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numbers come from

 

 
 

 


How is 'Spending Capacity' calculated?

This is a simple presentation of these important numbers, but this simplicity hides a lot of complexity. If you are working on a "How much can I spend?" plan (as opposed to a "How can I spend $X, net of tax?" plan), 'Spending Capacity' is the spending amount that, if followed through the plan with no deviation, would have the targeted risk of overspending/underspending

The example shown above targets a 20% chance of overspending and an 80% chance of underspending. (This is the center setting on the 'Income Setting' slider.)

 


To arrive at this 'Spending Capacity', Income Lab software incorporates all of the unique risks of the plan, including:

Different plans will have different risk profiles, and these risks will be different depending on your chosen capital market and inflation assumptions, as well as on a plan's longevity settings. However, these assumptions and the idiosyncrasies of the plan come together to define overspending and underspending risks for the plan. The software then finds a spending level with the desired mix of overspending/underspending risk.

 

How are Guardrails calculated?

The portfolio balances that would trigger a change in income are calculated by asking,

"At what portfolio balance would current spending reach risk levels that would call for a change?"


For example, if the example above calls for an increase in income (the upper guardrail) when the risk of underspending reaches 100%, the question becomes, "At what point would spending $5490/month have a 100% chance of underspending?". The answer in the example shown above is that, if instead of $1 million in the portfolio there were instead $1.05 million, the underspending risk would be too high and an increase in income would be called for.

In this example, the lower guardrail is reached when the risk of overspending reaches 75%. So, for the lower guardrail, the question is, "At what point would spending $5490/month have a 75% chance of overspending?" The answer in the example shown above is that, if instead of $1 million in the portfolio, there were instead $730,000 (a 27% decrease in the portfolio), overspending risk would be too high and a decrease in income would be called for.

As you can see, both questions ask what sort of change in portfolio balance would swing risk enough that an adjustment would be called for.

The amounts of adjustment, where these guardrails are to be hit, are calculated by asking, "Given that this change in portfolio balance has happened, what adjustment would the plan call for to move the risk away from the guardrail?" For example, the upper guardrail for this plan says that, if the risk of underspending reaches 100% we will adjust spending to reduce that to an 80% chance of underspending. In this case, that means spending would be increased to $5760/month.