Methodology

General principle

Each ViaVest tool is a simplified mathematical model designed for educational purposes. The goal is not to predict the future, but to illustrate the financial mechanisms at play and allow interactive exploration of key parameters.

Results do not constitute investment, financing or tax advice. For any significant financial decision, consult a licensed professional.

Calculator 01: Real Estate vs Stocks

Model

The simulator compares two net wealth trajectories over the same horizon, with the same starting capital and monthly budget:

• Buy scenario: starting capital serves as down payment, the property is mortgage-financed. The property value grows at the chosen annual appreciation rate (monthly compounding). The budget surplus after mortgage is invested in equities. Final net wealth is: property value minus remaining debt, plus accumulated equity portfolio.
• Rent scenario: starting capital is invested from day one. Each month, the difference between the budget and rent is reinvested. Final net wealth is the equity portfolio.

Assumptions and limitations

This model does not account for: imputed rental value, mandatory amortisation of the 2nd mortgage, maintenance costs (estimated at 1% of property value per year in some cantons), transfer taxes, agent fees, and inflation. These factors tend to slightly favour the equity scenario in major Swiss cities.

Calculator 02: Asset Allocation (Monte Carlo)

Monte Carlo method

The simulator generates 1,500 independent random trajectories. For each simulation year, an annual return is drawn from a normal (Gaussian) distribution:

• Mean: expected return of the allocation (weighted sum of returns per asset class)
• Standard deviation: volatility of the allocation (calculated assuming zero correlation between classes)

The pseudo-random number generator used is Mulberry32, with a fixed seed (123456789) to ensure reproducibility at equal parameters. Gaussian numbers are generated using the Box-Muller transform.

Return and volatility assumptions

Asset class	Expected return (annual)	Volatility (standard deviation)
Equities	6.8%	16.0%
Bonds	2.5%	5.5%
Cash	0.9%	0.6%

These parameters are based on long-term historical averages of global markets (MSCI World for equities, Bloomberg Global Aggregate for bonds) and do not guarantee future performance.

Limitations

The model does not account for: correlations between asset classes (they converge in crises), inflation, management fees (fund TER), taxes on dividends and capital gains, and periodic portfolio rebalancing.

Calculator 03: Pillar 3a

Tax model

The annual tax saving is calculated as: 3a contribution × estimated marginal tax rate. The marginal rate used is an approximation based on average cantonal schedules (cantonal and municipal + federal) for each of the four available cantons:

Canton	Base marginal rate (income ~CHF 100k)
Geneva (GE)	28.5%
Vaud (VD)	25.5%
Bern (BE)	22.5%
Zurich (ZH)	20.5%

For incomes above CHF 80,000, a slight correction is applied (up to +4 percentage points at CHF 280,000). These rates are approximations and may differ significantly from your actual rate depending on your municipality, personal situation and other deductions.

Long-term projections

The three curves represent: (1) the 3a savings account at the set interest rate, (2) the 3a investment account at the set return, (3) equivalent savings outside 3a (after tax, at the savings rate). The 2026 maximum is CHF 7,258 for employees with a 2nd pillar.

Calculator 04: BVG Capital or Pension

Model

The guaranteed monthly pension is calculated as: capital × conversion rate / 12. The simulator then compares:

• Pension scenario: both lines start at the same capital and decrease at their respective monthly rate. The pension capital decreases monthly by the pension amount (minus return). The invested capital decreases by the monthly withdrawal amount.
• Goal: illustrate when each capital source is depleted, and which option is better at your life expectancy.

Limitations

This model does not account for: tax on capital withdrawal (capital withdrawal tax, 5 to 15% depending on canton and amount), annual taxation of pension as ordinary income, survivor pensions (spouse, children), the AHV/AVS pension, and healthcare costs increasing with age. These factors strongly influence the comparison and depend entirely on personal circumstances.

Official sources

The regulatory data used in the tools comes from the following sources:

• FSIO (Federal Social Insurance Office): 3a maximums, BVG conversion rates
• Federal Tax Administration (FTA): general tax information
• FSO (Federal Statistical Office): demographic data and life expectancies
• IAZI: Swiss property price indices
• SNB: mortgage rate data

Update frequency

Legal parameters (3a maximums, BVG conversion rates, AHV retirement ages) are updated at each official change. Return assumptions are reviewed annually. Each page shows the date of last update.