Problems solved in full
-
$1,000,000 in a 60/40 blend across 1966 to 1995 with no withdrawals 5 steps
Show that the order of 30 years of returns cannot change the final pot, and then measure what the wobble inside them costs anyway. This is No withdrawals: $1,000,000 in a 60/40 blend across 1966 to 1995, nothing taken out, and the panel reporting the arithmetic mean of those years as 10.31%.
-
A year multiplies the pot by 1 + r and does nothing else to it. Run that 30 times and the whole retirement is a single product rather than a process.
-
Multiplication commutes, so reversing the list writes the same 30 factors in a different order and cannot change what they multiply to. The two curves in the chart cross and recross and still land on the same point, and the tool has no choice in the matter.
-
Multiply the factors out. This window nearly 16-folds the pot.
-
The compound growth rate is whatever single rate reproduces that product, so take the 30th root. It is not the average of the returns and it cannot be: one is built from a product, the other from a sum.
-
Now imagine a pot that earned exactly the panel's 10.31% every single year, with the same average and none of the variation. Compound it for the same 30 years and subtract.
Answer
$15,953,990, from either end of the sequence. The steady-10.31% pot finishes at $18,986,571 instead, so varying returns cost $3,032,581 without a single year's number being changed β 19% of what the portfolio actually ends with. That is why 9.67% is the honest figure and 10.31% is not: an average you could only have collected by never deviating from it was never available. The penalty scales with the square of the spread, so a portfolio twice as jumpy around the same average gives up roughly 4 times as much to it. Order is free here. Volatility never was.
-
-
Drawing 4% from $1,000,000 in a 60/40 blend across 1929 to 1958 6 steps
The same kind of sequence, but now $40,000 a year comes out of it. The window compounds at 6.58% and you are drawing 4%, which sounds like room to spare. This is Retiring into 1929: $1,000,000 in a 60/40 blend across 1929 to 1958, a first-year draw of 4% of the starting pot, rising 3% a year with prices.
-
A withdrawal rule fixes dollars, not a percentage. 4% of the starting million is $40,000, and every later year takes that same $40,000 raised by 3% compounding. The pot's own balance never enters the withdrawal again.
-
1929 returned -3.30% on the blend. Grow first, then subtract: the year's income comes out of what the year's market left behind.
-
Unroll the recurrence and it separates into a product term and a sum term. The product is the saver's, untouched. In the sum, each withdrawal is multiplied only by the years that come after it β a 1929 withdrawal carries 29 subsequent factors, a 1958 one carries none. Reversing the sequence leaves the product alone and rebuilds the sum from scratch.
-
You already have the product without touching the data. Compound growth is defined as its 30th root, so raise the panel's figure back up.
-
Compute the sum both ways round. Identical factors, identical withdrawals; all that changed is which factors sit behind which withdrawal. Forward, the withdrawals carry a combined weight of 196.47. Reversed, 82.09.
-
The sum is proportional to the first year's draw, so setting the final value to zero and solving for that draw is a rearrangement, not a search. It gives the largest opening withdrawal each order can survive.
Answer
Forward the pot is exhausted in 1950; reversed, the identical 30 years finish at $3,484,161. The break-even opening draw is $34,444 one way round and $82,438 the other β 3.44% against 8.24%, a factor of 2.39 out of a reshuffle. That ratio is the quantity a retirement plan actually turns on, and neither headline percentage can supply it: the mean 7.63% and the compound growth 6.58% are both constructed to ignore order. It also disposes of the intuition this problem opened with. Drawing 4% from something growing at 6.58% is not a 2.58-point margin, because 4% is a percentage exactly once. After that it is $40,000 with an inflation escalator attached. By the fifth year that draw has grown to $45,020, and the forward pot it comes out of is $459,742 while the reversed pot at the very same point is $1,298,083 β the identical rule, biting at 9.79% in one order and 3.47% in the other.
-
Learning path
Risk, measured
References (4)
- The withdrawal-rate question this tool is a demonstration of, tested against historical sequences rather than averages: P. L. Cooley, C. M. Hubbard and D. T. Walz, "Comparative Analysis of Retirement Portfolio Success Rates." Financial Services Review 12(2), 115β128, 2003.
- Sequence-of-returns risk named and measured, which is the effect the two paths on this page differ by: A. Soni, "The Role of Annuities in Managing Sequence of Returns Risk Approaching and in Retirement." The Journal of Retirement 11(4), 26β39, 2023.
- Ruin as the quantity of interest rather than a final balance β the reason this tool reports the year the pot is exhausted: D. Daraei and K. Sendova, "Determining Safe Withdrawal Rates for Post-Retirement via a Ruin-Theory Approach." Risks 12(4), 70, 2024.
- And the standing objection to any single historical path, including the ones drawn here: M. E. Drew and A. Walk, "Just How Safe are βSafe Withdrawal Ratesβ in Retirement?" Financial Planning Research Journal 1(1), 22β32, 2015.