Life-Cycle Finance: A Financial Plan for Your Entire Life

In July 2026, the Rational Reminder podcast interviewed Dr. Paul Kaplan, retired director of research at Morningstar Canada and co-author of Lifetime Financial Advice, about the question at the center of financial planning: how much should you spend each year of your life?¹ The branch of economics that answers it is called life-cycle finance. It treats saving, investing, insurance, annuities, and retirement spending as one connected problem with one objective: smoothing your consumption over your entire life, so your standard of living transitions gently between working years and retirement instead of jumping or collapsing.

Most retirement planning does something else. It stitches together disconnected rules of thumb: save 15% of income, hold your age in bonds, withdraw 4% a year. Each rule answers its own small question and none of them talk to each other. Life-cycle finance replaces the patchwork with a single optimization, and its two outputs are the two decisions that matter: how much to consume each year and how to invest what remains.

The theory won four Nobel Prizes

Life-cycle finance has an unusually deep academic pedigree. Franco Modigliani and Richard Brumberg formalized the life-cycle hypothesis in 1954: households choose consumption based on lifetime resources, saving in high-income years to fund low-income ones.² Milton Friedman’s permanent income hypothesis (1957) made the same core argument from a different direction: spending tracks expected lifetime income, and windfalls or shortfalls get smoothed rather than spent or absorbed immediately.³ In 1969, Paul Samuelson and Robert Merton solved the joint consumption-and-portfolio problem, in discrete and continuous time respectively, establishing how a rational investor should divide wealth between spending, risky assets, and safe assets at every age.^4,5

Modigliani won the Nobel Prize in 1985, in large part for the life-cycle hypothesis. Friedman won in 1976, Samuelson in 1970, and Merton in 1997. Kaplan’s point on the podcast is the paradox that follows: a half-century of Nobel-recognized theory about how households should plan their finances has barely penetrated the financial planning software that households and their advisors actually use. The tools are comprehensive about taxes and account types while the economic engine underneath remains a collection of ad hoc rules.¹

Your economic balance sheet

The life-cycle framework starts by rebuilding your balance sheet. A company’s balance sheet lists everything it owns and owes; yours should too. On the asset side sit your financial assets plus an entry most net worth statements omit entirely: human capital, the present value of all the labor income you have yet to earn. On the liability side sits the present value of your future non-discretionary spending, the food, housing, healthcare, and insurance you must fund no matter what. What remains is your economic net worth, the quantity a life-cycle model plans with.⁶

For most people under 50, human capital is the largest asset they own. A 35-year-old earning $150,000 with 30 working years ahead holds several million dollars of present-valued future earnings, typically dwarfing their portfolio. Ibbotson, Milevsky, Chen, and Zhu built an entire CFA Institute monograph around this observation in 2007: asset allocation, life insurance, and annuity decisions all change once human capital is on the balance sheet, because human capital starts enormous and declines toward zero at retirement while financial capital does the reverse.⁷

Are you a stock or a bond?

Human capital has risk characteristics, and they should shape your portfolio. Moshe Milevsky’s framing has become the standard teaching example: a tenured professor’s future income is steady and nearly guaranteed, so her human capital behaves like a large bond holding; a stockbroker’s income rises and falls with the market, so his human capital behaves like leveraged equity.⁸ Given identical questionnaire answers, the professor can afford a far more aggressive portfolio than the broker, because her total balance sheet already holds an enormous bond-like position. The broker holding a 90% equity portfolio on top of equity-like human capital is running concentrated risk he probably never chose deliberately.

Bodie, Merton, and Samuelson added a second dimension in 1992: the flexibility of your labor supply. Someone who can work more hours, delay retirement, or return to work after a market crash holds a valuable option, and that option justifies taking more investment risk earlier in life.⁹ A tech worker with in-demand skills and a paid-off house has more risk capacity than her portfolio statement suggests; a 64-year-old in a physically demanding job with no re-employment prospects has less.

Risk tolerance and risk capacity are different measurements

This balance-sheet view cleanly separates two concepts the industry routinely blends. Risk tolerance is a preference: how much volatility you can emotionally and behaviorally withstand without abandoning the plan. Risk capacity is a constraint: how much loss your balance sheet can objectively absorb, given your human capital, your liabilities, and your time horizon. A typical risk questionnaire asks about both and compresses the answers into a single score, which Kaplan argues is a category error. Blending a preference with a constraint produces a number with no clear meaning, and it cannot tell the tenured professor with low tolerance and high capacity apart from the stockbroker with high tolerance and low capacity.¹ The Idzorek-Kaplan model keeps them separate: tolerance enters as a utility parameter, capacity emerges from the balance sheet, and the optimization reconciles the two.¹⁰

Spending is the model’s output

The deepest difference between life-cycle planning and conventional planning is where spending enters the analysis. A conventional plan takes your spending as an input: you state what you spend, and the software checks whether the money survives. A life-cycle model inverts this. You supply your balance sheet, your preferences (how much you value spending now versus later, how flexible you can be, how much you care about bequests), and your circumstances (mortality, market assumptions). The model then tells you the consumption path that maximizes your lifetime well-being subject to the budget you have.⁶

In the Idzorek-Kaplan formulation this collapses to a formula with two moving parts. Your sustainable spending equals your economic net worth divided by an annuity-like divisor that weights each future year by your probability of being alive to enjoy it. And your planned spending grows (or shrinks) at a rate set by the gap between expected returns and your personal impatience. Because the odds of reaching 105 are small, survival weighting reserves little for those years and releases that money into your 60s and 70s, when you are far more likely to be alive and able to use it. Kaplan calls this the rescheduling factor.¹¹

Where the 4% rule comes from

Measured against this framework, the most famous rule in retirement planning looks strange. William Bengen’s 1994 study found that a retiree holding 50% stocks and 50% intermediate Treasuries could have withdrawn an inflation-adjusted 4% of their starting portfolio through every historical 30-year period since 1926 without running out.¹² The Trinity study popularized the same approach as a table of historical success rates.¹³ Both are backtests. Neither derives from a theory of what a retiree is trying to achieve, which is Kaplan’s core critique: rerun the backtest on different data and you get a different number, because there is no economics underneath, only history.¹

The research since has been unkind to the rule from both sides. Scott, Sharpe, and Watson showed in 2009 that a fixed real withdrawal funded by a volatile portfolio is inefficient by construction: the retiree pays for spending she will never do in the bad scenarios and accumulates unspent surpluses in the good ones.¹⁴ David Blanchett showed that real retiree spending is not constant anyway; it declines roughly 1% per year in real terms through most of retirement before late-life medical costs bend it back up, a pattern he called the retirement spending smile.¹⁵ And when Anarkulova, Cederburg, O’Doherty, and Sias replaced the US-only historical record with a broad sample of developed markets, the “safe” constant-real rate for a 65-year-old dropped to roughly 2.7%, a figure Rational Reminder listeners will recognize from Ben Felix’s coverage.¹⁶

The lifecycle answer to sequence risk is adjustment rather than ruin. A retiree following the closed-form rule recalculates spending as markets move: bad early returns mean spending drifts down, good returns mean it drifts up, and the portfolio cannot hit zero while its owner is alive because spending is always a fraction of what remains. Kaplan’s question is fair: why run a known risk of total depletion to defend a fixed number that economic theory never endorsed in the first place?¹

Run consumption smoothing on your own numbers

The calculator below implements the core of the lifecycle consumption rule: a survival-weighted economic balance sheet, a spending level solved as an output, and a comparison against a 4% rule funded from the same retirement pot. Watch two things as you move the sliders. First, the implied savings rate: it is a residual, so it responds to your whole balance sheet rather than sitting at a fixed 15%. Second, drag the expected return down and watch the 4% path hit zero while the lifecycle path bends and survives.

Annuities and the mortality-credit trade

Lifetime planning has to confront an awkward fact: you do not know how long you will live. Self-insuring longevity means holding enough assets to fund age 100 even though you will probably die around 85, which forces underspending in the years you are most likely to be alive. Annuities solve this through risk pooling. In an annuity pool, the capital of members who die early funds the payments of members who live long, and that transfer, which Milevsky popularized as mortality credits, gives survivors a return no conventional asset can match at advanced ages.¹⁷

The theory here is old and strong. Menahem Yaari proved in 1965 that a retiree facing only longevity risk, with no bequest motive and access to fairly priced annuities, should annuitize all of her wealth.¹⁸ Real markets soften that result considerably: actual annuities carry fees and adverse selection, most are nominal and therefore exposed to inflation, people hold real bequest motives, and late-life medical shocks demand liquidity that an annuity cannot provide. Economists call the resulting gap between theory (annuitize heavily) and behavior (almost nobody voluntarily annuitizes) the annuity puzzle.¹⁷ The lifecycle framework treats partial annuitization and term life insurance as instruments in the same optimization: life insurance protects your bequest while human capital is still your main asset, and annuities extend consumption when longevity is the main risk left.⁶

Where lifecycle models fall short

A model this elegant deserves its caveats stated plainly.

• The preference parameters are hard to measure. The model needs your subjective discount rate, your elasticity of intertemporal substitution, and your bequest weights. These are real preferences, but no validated questionnaire reliably elicits them yet; Idzorek and Kaplan themselves describe their sample profiling questions as a starting point rather than a finished instrument.⁶
• Variable spending is behaviorally expensive. The optimal plan cuts spending after bad markets. Households with high fixed costs, or a low tolerance for telling family the vacation budget shrank 12% this year, may rationally accept some theoretical inefficiency for the predictability of a floor. Blanchett’s data shows retiree spending already declines in real terms, so some flex is normal, but a mortgage payment does not flex.¹⁵
• Human capital is hard to value. Your future earnings are not a bond you can look up on a screen. Industry, tenure risk, health, and correlation with equity markets all enter the estimate, and reasonable people will disagree about the beta of a marketing career.
• Simplified taxes. The published model handles asset location across taxable and tax-advantaged accounts at its second level, but any tractable implementation compresses the tax code. US retirees with large traditional IRAs still need RMD and Roth conversion analysis on top.⁶

Our recommendation is to adopt the framework even if you never estimate a utility parameter. Treating your career as an asset with a risk profile, separating tolerance from capacity, planning spending from your whole balance sheet, and using a spending rule that responds to markets are each individually valuable, and all four survive any disagreement about the model’s fine print. In practice, amortization-style rules such as VPW, or guardrails rules that cut and raise spending at trigger points, capture most of the lifecycle benefit with far less machinery; Summitward’s retirement simulator models both alongside the constant-real baseline.

Run the full model yourself

Kaplan built a spreadsheet implementing Part I of the book, demonstrated it on the episode, and the CFA Institute Research Foundation hosts it as a free download alongside the book itself, which is also free.⁶ It runs in desktop Excel with macros enabled, the VBA source is open for inspection, and it is licensed for educational, non-commercial use. It models everything this guide’s simplified calculator omits: Gompertz mortality with adjustable longevity, salary curves by education, Social Security, annuity fractions, life insurance, optimal bequests, and probabilistic fan charts for consumption and wealth. If this guide’s ideas landed, an afternoon in that spreadsheet is the best follow-up available.

Frequently asked questions

What is life-cycle finance?

Life-cycle finance is the branch of economics that studies how a person should consume, save, invest, insure, and annuitize across their whole life to smooth their standard of living. Its foundations were laid by Modigliani, Friedman, Samuelson, and Merton between 1954 and 1971, and its central output is a consumption plan plus an asset allocation, both derived from one optimization rather than separate rules of thumb.

Is the 4% rule based on economic theory?

No. It comes from backtests of US historical returns (Bengen 1994 and the Trinity study), and it changes whenever the data sample changes. Economic analysis has criticized it from two directions: it is an inefficient way to fund fixed spending (Scott, Sharpe, and Watson), and broader international data supports a much lower constant-real rate, around 2.7%. Lifecycle models replace the fixed rate with spending that adjusts to markets and remaining life expectancy.

What is human capital in investing?

Human capital is the present value of your expected future labor income. For most people under 50 it is their largest asset. Its risk character matters as much as its size: stable, bond-like earnings (tenured professor, government employee) support a more aggressive portfolio, while market-correlated earnings (stockbroker, startup employee paid in equity) call for a more conservative one.

What is the difference between risk tolerance and risk capacity?

Risk tolerance is your willingness to bear volatility, a psychological preference. Risk capacity is your ability to absorb losses, an objective feature of your balance sheet driven by human capital, liabilities, and horizon. A sound plan measures them separately; questionnaires that average them into one score can recommend the same portfolio to people whose situations argue for opposite ones.

Should I annuitize part of my retirement savings?

Theory says annuities deserve more consideration than they get: mortality credits are a return source nothing else replicates at advanced ages, and Yaari’s classic result shows full annuitization is optimal under idealized assumptions. Practice argues for moderation: fees, inflation exposure on nominal products, bequest motives, and liquidity needs all cut against annuitizing heavily. Delaying Social Security, which is an inflation-indexed annuity purchased at actuarially favorable terms, is usually the strongest first move.

Where can I get the Kaplan-Idzorek spreadsheet and book?

Both are free from the CFA Institute Research Foundation. The book page for Lifetime Financial Advice: A Personalized Optimal Multilevel Approach links the PDF and the supplementary Excel lifecycle model. The spreadsheet requires desktop Excel with macros enabled and is for educational, non-commercial use.

Related guides

• Safe Withdrawal Rate: Why the 4% Rule Isn’t Enough covers the withdrawal-rate evidence in depth; this guide supplies the economic framework that explains why fixed rates were never the right objective.
• Lifecycle Asset Allocation works out the asset-allocation half of the lifecycle problem: why large, bond-like human capital justifies more equity when young.
• Human Capital Risk for Tech Workers applies the stock-or-bond question to a career where salary, equity compensation, and the sector all move together.
• Lifecycle Consumption Smoothing for Professional Students applies the same framework to the accumulation edge case of near-zero income and high expected earnings.
• Die With Zero vs. FIRE explores the same tension between consuming while alive and holding wealth defensively, from the popular-book side.
• Should Retirees With Social Security or a Pension Hold More Stocks? is a worked risk-capacity example: guaranteed income is a bond-like asset on the economic balance sheet.
• Understanding Your CEFR Score explains Summitward’s funded-ratio metric, which measures the liability side of the economic balance sheet described here.

Sources

1. Rational Reminder Podcast, Episode 417 (July 2026). “A Financial Plan For Your Entire Life”, with Dr. Paul Kaplan. Hosts Benjamin Felix and Cameron Passmore.
2. Modigliani, F. & Brumberg, R. (1954). “Utility Analysis and the Consumption Function: An Interpretation of Cross-Section Data.” In Post-Keynesian Economics, Rutgers University Press. See also Modigliani’s Nobel lecture, “Life Cycle, Individual Thrift and the Wealth of Nations” (1985).
3. Friedman, M. (1957). A Theory of the Consumption Function. Princeton University Press. The permanent income hypothesis.
4. Samuelson, P. A. (1969). “Lifetime Portfolio Selection by Dynamic Stochastic Programming.” The Review of Economics and Statistics 51(3), 239-246.
5. Merton, R. C. (1969). “Lifetime Portfolio Selection under Uncertainty: The Continuous-Time Case.” The Review of Economics and Statistics 51(3), 247-257. Extended in Merton (1971), Journal of Economic Theory 3(4), 373-413.
6. Idzorek, T. M. & Kaplan, P. D. (2024). Lifetime Financial Advice: A Personalized Optimal Multilevel Approach. CFA Institute Research Foundation. Free PDF and supplementary Excel lifecycle model at the same page.
7. Ibbotson, R. G., Milevsky, M. A., Chen, P., & Zhu, K. X. (2007). Lifetime Financial Advice: Human Capital, Asset Allocation, and Insurance. Research Foundation of CFA Institute.
8. Milevsky, M. A. (2012). Are You a Stock or a Bond? Identify Your Own Human Capital for a Secure Financial Future. FT Press.
9. Bodie, Z., Merton, R. C., & Samuelson, W. F. (1992). “Labor Supply Flexibility and Portfolio Choice in a Life Cycle Model.” Journal of Economic Dynamics and Control 16(3-4), 427-449.
10. Kaplan, P. D. & Idzorek, T. M. (2024). “The Importance of Joining Lifecycle Models with Mean-Variance Optimization.” Financial Analysts Journal 80(4), 11-17.
11. Kaplan, P. D. & Idzorek, T. M. (2025). “A Hybrid Lifecycle Net Worth Optimization Model.” Financial Planning Review.
12. Bengen, W. P. (1994). “Determining Withdrawal Rates Using Historical Data.” Journal of Financial Planning 7(4), 171-180.
13. Cooley, P. L., Hubbard, C. M., & Walz, D. T. (1998). “Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable.” AAII Journal 20(2), 16-21.
14. Scott, J. S., Sharpe, W. F., & Watson, J. G. (2009). “The 4% Rule—At What Price?” Journal of Investment Management 7(3), 31-48.
15. Blanchett, D. M. (2014). “Exploring the Retirement Consumption Puzzle.” Journal of Financial Planning 27(5), 34-42.
16. Anarkulova, A., Cederburg, S., O’Doherty, M. S., & Sias, R. W. (2022). “The Safe Withdrawal Rate: Evidence from a Broad Sample of Developed Markets.” SSRN working paper; accepted at Journal of Pension Economics and Finance.
17. Hershfield, H. E., Shu, S., Brown, J. R., Hurwitz, A., Milevsky, M. A., Mitchell, O. S., & Toland, T. (2026). “The Annuity Puzzle Revisited: Barriers, Behavior, and Policy Paths to Lifetime Income.” NBER Working Paper 35145. Why consumers rarely buy annuities despite the theoretical case for them.
18. Yaari, M. E. (1965). “Uncertain Lifetime, Life Insurance, and the Theory of the Consumer.” The Review of Economic Studies 32(2), 137-150.