How GoldenRun Works

The methodology behind your retirement projections.

Projection Engine

GoldenRun runs a year-by-year simulation from your current age through the end of your plan (typically age 95). Each year, the engine calculates your income, expenses, taxes, savings contributions, investment growth, and withdrawals.

During your working years, your salary grows at the rate you specify, and contributions flow into each account according to your settings. Employer matches are applied up to the match limit. After retirement, the engine determines how much to withdraw from your accounts to cover expenses, following your chosen withdrawal strategy.

Investment returns are applied to each account based on its expected return rate. All balances compound annually. The engine tracks pre-tax, Roth, and taxable accounts separately because withdrawals from each type have different tax consequences.

Tax Calculations

GoldenRun models federal income taxes using the current progressive bracket structure. State taxes are estimated based on your state of residence. The engine accounts for the different tax treatment of each account type:

• Pre-tax accounts (401(k), Traditional IRA): Contributions reduce taxable income; withdrawals are taxed as ordinary income.
• Roth accounts (Roth IRA, Roth 401(k)): Contributions are after-tax; qualified withdrawals are tax-free.
• Taxable accounts (brokerage, savings): Growth and withdrawals may generate capital gains taxes.
• HSA: Tax-deductible contributions, tax-free growth, and tax-free withdrawals for qualified medical expenses.

Social Security benefits are taxed based on combined income thresholds — up to 85% of benefits may be taxable depending on your total income. Tax brackets are inflation-adjusted in the projection.

Social Security Modeling

You enter your estimated monthly Social Security benefit (available on ssa.gov) and your planned claiming age. Benefits begin at your claiming age and continue for life. Claiming earlier than your full retirement age (typically 67) permanently reduces your monthly benefit, while delaying to age 70 increases it by about 8% per year.

The Pro Social Security Optimizer compares the total lifetime income from claiming at different ages, accounting for the time value of money and your life expectancy. For couples, it analyzes spousal benefit strategies to find the combination that maximizes household income.

Monte Carlo Stress Testing

A single projection assumes steady returns every year — but real markets are volatile. Monte Carlo simulation tests your plan against randomized sequences of good and bad years.

GoldenRun runs 1,000 simulations. In each one, annual market returns are drawn from a distribution calibrated to historical stock and bond performance (mean ~7% real return, standard deviation ~15% for equities). The sequence of returns matters — a market crash early in retirement is far more damaging than one late in retirement (sequence-of-returns risk).

Your success rate is the percentage of simulations where your money lasted through your entire plan. A rate above 80% is generally considered strong. The results also show the range of outcomes — best case, median, and worst case — so you can understand the spread of possibilities, not just the average.

Withdrawal Strategies

The order in which you draw from different account types in retirement can significantly affect how long your money lasts and how much you pay in taxes. GoldenRun models three strategies:

• Conventional: Draw from taxable accounts first, then pre-tax, then Roth. This is the most common approach and preserves tax-free Roth growth for last.
• Roth-First: Draw from Roth accounts first. This can make sense if you expect tax rates to be lower in the future or want to preserve pre-tax accounts for heirs.
• Tax-Optimized: Dynamically fills lower tax brackets from pre-tax accounts while drawing from Roth and taxable accounts to cover the rest. This approach minimizes total lifetime taxes by smoothing taxable income across years.

The Withdrawal Strategy Optimizer runs your full projection under each strategy and compares total runway (years until money runs out) and total lifetime taxes paid.

Key Assumptions & Limitations

• Inflation: Defaults to 2.5% annually. Expenses, tax brackets, and Social Security benefits are adjusted for inflation each year.
• Investment returns: You set the expected return for each account. Returns are applied uniformly each year in the base projection (Monte Carlo adds variability).
• Healthcare costs: Modeled separately for pre-Medicare (before 65) and post-Medicare periods. Costs grow with healthcare inflation.
• Life expectancy: Defaults to age 95. You can adjust this — planning to a later age is more conservative.
• Not financial advice: GoldenRun is a planning tool, not a licensed financial advisor. The projections are estimates based on the assumptions you provide. Tax laws change, markets are unpredictable, and personal circumstances vary. Consider consulting a qualified financial professional for major decisions.