Spending Parameters

Endowment Parameters
$
%
%
%
Rule-Specific Settings
years
% of prior
% of prior
Additional Settings
$
years
Spending Rule Formulas
Simple: Rate × PostReturnMV
Rolling Avg: Rate × Avg(MV, N yrs)
Yale: w × S(t-1) × (1+inf) + (1-w) × Rate × MV
Cap-Floor: Rate × MV, clamped to [Floor, Cap]
MV = Post-Return Market Value | S(t-1) = Prior Year Spending | w = Weight on Prior | inf = Inflation
Ryan O'Connell, CFA
Calculator by Ryan O'Connell, CFA

Spending Analysis

Year 1 Spending $5,000,000 Sustainable
Terminal Endowment --
Total Spending --
Avg Spending / Year --
Spending Volatility --
Real Growth (CAGR) --
* Real Growth includes external contributions

Rule Comparison

* Real Growth includes external contributions

Spending Path

Simple
Rolling Avg
Yale
Cap-Floor

Year-by-Year Projection

Formula Breakdown

Model Assumptions
  • Investment returns are constant (expected return achieved every year)
  • No stochastic modeling of returns, spending, or inflation
  • Annual contributions and inflation rate are constant over the horizon
  • Spending is withdrawn after investment returns are applied (end-of-year)
  • Year 0 is a pure snapshot: seed spending is shown for reference but not deducted from the endowment
  • Yale-Style Smoothing uses current-year post-return market value (not lagged); actual Yale endowment timing may differ
  • Rolling average uses available years when fewer than the window size exist
  • If endowment is depleted, actual spending is capped at available funds and simulation stops
  • Real Growth uses the exact Fisher formula: (1 + nominal CAGR) / (1 + inflation) - 1

For educational purposes. Not financial advice. Market conventions simplified.

Understanding Endowment Spending Rules

What is an Endowment Spending Rule?

An endowment spending rule (or spending policy) determines how much an endowment distributes each year to fund operations, scholarships, research, or other purposes. The fundamental challenge is balancing two competing goals: providing adequate current funding while preserving the endowment's real (inflation-adjusted) purchasing power for future generations. This is known as the principle of intergenerational equity.

The Four Spending Rules

Simple Spending Rate

Formula: Spending = Rate × PostReturnMV
Applies a fixed percentage to current market value. Simple and transparent, but spending fluctuates directly with investment returns, creating budget volatility.

Rolling Average

Formula: Spending = Rate × Average(MV over N years)
Smooths spending by averaging market values over a window (typically 3-5 years). Reduces volatility but lags behind market movements.

Yale-Style Smoothing

Formula: S(t) = w × S(t-1) × (1+inf) + (1-w) × Rate × MV
Blends inflation-adjusted prior spending (weight w) with current endowment value (weight 1-w). Used by Yale, Stanford, and many large endowments. Produces very smooth, predictable distributions.

Cap-Floor Policy

Formula: Spending = Rate × MV, clamped to [Floor%, Cap%] of prior spending
Starts with the simple rule but constrains year-over-year changes. Prevents both excessive spending in bull markets and painful cuts in downturns.

Spending Volatility vs. Endowment Sustainability

There is a fundamental trade-off between spending smoothness and responsiveness to market conditions:

  • More smoothing (Yale with high w, narrow cap-floor bands) provides budget predictability but can lead to over-spending in prolonged downturns or under-spending in prolonged bull markets
  • Less smoothing (simple rule, wide cap-floor bands) keeps spending aligned with actual endowment performance but creates budget volatility that can disrupt operations

The spending volatility metric (standard deviation of year-over-year spending changes) quantifies this trade-off. Lower volatility means more predictable budgets.

Key Sustainability Condition
Real Return = (1 + Nominal Return) / (1 + Inflation) - 1
If Real Return > Spending Rate, endowment grows in real terms
This is a necessary (but not sufficient) condition for long-term sustainability
Important: This calculator uses deterministic (constant) returns. Real endowments experience volatile returns, and the sequence of returns matters — poor early returns combined with fixed spending can permanently impair an endowment even if average returns are adequate. Consider Monte Carlo simulation for a more realistic assessment.

Frequently Asked Questions

An endowment spending rule is a policy that determines how much an endowment distributes each year to fund operations, scholarships, or other purposes. The goal is to balance current spending needs with preserving the endowment's purchasing power for future generations. Common rules include a simple percentage of market value, rolling averages, Yale/Stanford-style smoothing, and cap-floor policies. The choice of spending rule affects both the predictability of annual distributions and the long-term sustainability of the endowment.

The Yale/Stanford spending rule (also called the smoothing rule) blends two components: (1) last year's spending adjusted for inflation, weighted by w, and (2) the target spending rate applied to current post-return market value, weighted by (1-w). The formula is: Spending(t) = w × [Spending(t-1) × (1 + inflation)] + (1-w) × [Rate × PostReturnMV(t)]. A typical weight of 0.80 means 80% of spending is based on the inflation-adjusted prior year and 20% on current endowment value, providing smooth, predictable distributions while still responding gradually to changes in endowment value. This calculator implements the Yale-style variant using current-year post-return market value, consistent with the MTMP textbook presentation; actual university endowment policies may use lagged market values or other timing conventions.

The simple spending rule applies a fixed percentage to the current year's post-return market value: Spending = Rate × PostReturnMV. This is straightforward but produces volatile spending that fluctuates with market returns. The rolling average rule applies the same rate to the average market value over a window of N years: Spending = Rate × Average(PostReturnMV over N years). This smooths spending by dampening the impact of any single year's returns, though it lags behind market movements. The rolling average is a middle ground between the simple rule's volatility and more sophisticated smoothing approaches.

A cap-floor policy starts with the simple spending calculation (Rate × PostReturnMV) but constrains year-over-year changes. If spending would increase more than the cap (e.g., 105% of prior year), it is capped. If it would decrease more than the floor (e.g., 95% of prior year), a floor is applied. This prevents both excessive spending in bull markets and painful cuts in bear markets, providing budget stability while still responding to endowment performance over time. The tighter the bands, the smoother the spending — but also the slower the adjustment to changing market conditions.

Most university and foundation endowments target a spending rate between 4% and 5.5% of market value. The most common target is 5%. This rate is designed to allow the endowment to maintain its real (inflation-adjusted) value over time while providing meaningful annual distributions. The actual sustainable rate depends on expected investment returns, inflation, and the specific spending rule used. If expected real returns (nominal return minus inflation) exceed the spending rate, the endowment should grow in real terms over long horizons.

Endowment spending is sustainable when the real (inflation-adjusted) value of the endowment is maintained or growing over time. Key indicators include: (1) the spending rate is below the expected real return, (2) the terminal endowment value exceeds the initial value in real terms, (3) the real growth rate of spending is positive, and (4) the endowment does not deplete during the projection horizon. This calculator's Real Growth metric shows the annualized inflation-adjusted growth rate of the endowment, with positive values indicating sustainability. When annual contributions are included, Real Growth may overstate sustainability — the calculator flags these cases as "Contribution-Dependent." Note that deterministic projections can be misleading — volatile real-world returns mean sustainability also depends on return sequence risk.
Disclaimer

This calculator is for educational purposes only and uses simplified, deterministic assumptions. Actual endowment management involves stochastic return modeling, spending policy committees, and consideration of donor restrictions, tax implications, and regulatory requirements. This tool should not be used for actual endowment spending decisions.

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Course by Ryan O'Connell, CFA, FRM

Portfolio Analytics & Risk Management Course

Master portfolio theory and risk management from fundamentals to advanced analytics. Covers modern portfolio theory, risk metrics, performance evaluation, and factor models.

  • Endowment management and spending policy analysis
  • Modern Portfolio Theory and efficient frontier construction
  • Risk metrics: VaR, CVaR, drawdown analysis
  • Hands-on exercises with real portfolio data
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