That question is also relatively easy to answer: https://www.portfoliovisualizer.com/backtest-portfolio?s=y&timePeriod=4&startYear=1998&firstMonth=1&endYear=201

That question is also relatively easy to answer: https://www.portfoliovisualizer.com/backtest-portfolio?s=y&timePeriod=4&startYear=1998&firstMonth=1&endYear=2018&lastMonth=12&calendarAligned=true&includeYTD=false&initialAmount=10000&annualOperation=1&annualAdjustment=10000&inflationAdjusted=true&annualPercentage=0.0&frequency=4&rebalanceType=1&absoluteDeviation=5.0&relativeDeviation=25.0&leverageType=0&leverageRatio=0.0&debtAmount=0&debtInterest=0.0&maintenanceMargin=25.0&leveragedBenchmark=false&reinvestDividends=true&showYield=false&showFactors=false&factorModel=3&portfolioNames=false&portfolioName1=Portfolio+1&portfolioName2=Portfolio+2&portfolioName3=Portfolio+3&symbol1=SPY&allocation1_1=100 https://www.portfoliovisualizer.com/backtest-portfolio?s=y&t... The "rate of return" isn't quite as simple to define when you're talking about multiple contributions over time. The most straightforward approach is to look at it as a weighted average, and the exact value depends on how you do the weighting. But in this case, it's in the ballpark of 7%/year nominal, which is probably 4-5%/year after inflation. As you can see, you get a big boost (at least in this cherry-picked example) by continuing to invest through the downturn.