The Core Four — Portfolio Simulator
The four building blocks of almost every portfolio: US stocks, developed markets, emerging markets, and bonds. Set your mix and see the range of outcomes. A single "you'll have $X" number is a guess: real markets are random, so this runs 2,000 market paths and shows the range. Everything runs in your browser; nothing is sent anywhere.
Your plan
Allocation 100%
Overweight your own market: pick a country and give it a %, then trim the others so the total stays 100%. Uses that region's ~30-year USD return and volatility.
Set any asset to 0. Your allocation must total 100% before you run.
Saved only in this browser (no account, nothing uploaded). Load one to restore your allocation and plan.
Saved plans
10th – 90th percentile
the range 8 in 10 simulations landed in
Median: half did better, half worse (a typical outcome)
High: top 10% (a strong market) · Low: bottom 10% (a weak market)
What each asset means
US stocks: The entire US stock market — every American public company, from Apple down to the smallest. The core engine of most portfolios.
Developed ex-US: Large companies in developed countries outside the US — Europe, Japan, Australia, Canada. Diversifies away from a single country.
Emerging markets: Companies in faster-growing, less-established economies — China, India, Brazil, Taiwan and more. Bigger swings than developed markets.
Bonds: US investment-grade bonds — loans to the government and solid companies that pay interest. Lower return, but far steadier than stocks.
The data behind it, and how the simulation works
Each simulated month, your portfolio earns a random return based on its blended expected return and volatility. We do that 2,000 times and report the range.
1. Blend your mix into one return + volatility (assuming annual rebalancing): μₚ = Σ wᵢ·μᵢ, σₚ = √(ΣΣ wᵢwⱼσᵢσⱼρᵢⱼ).
2. Annual → monthly: m = (1+μₚ)^(1/12) − 1, s = σₚ/√12.
3. Each month, draw a random return from a lognormal calibrated to (m, s).
4. Grow and add contributions: Bₜ₊₁ = (Bₜ + contribution) × (1 + rₜ), until the "keep investing for" cutoff.
5. Repeat 2,000×; sort the ending values; report the 10th / 50th / 90th percentiles. "Today's dollars" divides by (1.025)^years.
The numbers used (nominal annual return + volatility, ~30-yr history where available):
| Asset | Proxy | Return | Volatility |
|---|---|---|---|
| US stocks | CRSP US Total Market (VTI) | 10.5% | 15.7% |
| Developed ex-US | MSCI EAFE (EFA) | 5.9% | 16.4% |
| Emerging markets | MSCI EM (EEM) | 6.5% | 22.2% |
| Bonds | Bloomberg US Aggregate (BND) | 4.0% | 4.2% |
- Method: each figure is the long-run average from roughly 30 years of history (about 1996–2026 for US, developed, emerging, bonds, REITs and gold; Bitcoin uses ~10 years, deliberately moderated well below its short history).
- Sources: index total-return series (VTI, EFA, EEM, BND, VNQ), spot gold and Bitcoin via lazyportfolioetf.com, cross-checked against S&P 500, MSCI and Bloomberg index fact sheets.
- Small/large and growth/value sub-classes are estimated from the matching Russell and MSCI indices; correlations are approximate long-run values.
- Home-country tilt: ~30-year USD total returns (unhedged, so they include currency moves): Canada 8.6% / 20.1%, UK 6.5% / 16.6%, Australia 7.6% / 21.7%, Europe 7.3% / 18.0% (via lazyportfolioetf.com).
- These are historical assumptions, not forecasts.
Illustrative, not financial advice. See the disclaimer.