Key takeaways
- The contribution rate is the input you control completely. Returns are not.
- Doubling the monthly amount doubles the ending balance exactly, because the arithmetic is linear in contributions.
- Early years are worth more than late ones, so a raise directed into savings today outperforms a larger one later.
- Chasing an extra point of return is harder, riskier and usually smaller than simply contributing more.
The only input you actually control
A projection has three main dials. How much you put in, how long it compounds, and what it earns. You set the first with a decision. You influence the second by starting sooner. The third is not yours.
Most people spend their attention on the dial they cannot turn.
What doubling the contribution does
Contributions enter the arithmetic linearly, which makes this unusually easy to reason about. Double the deposit and you double the result.
At $250 a month for thirty years at 7 percent you finish with about $292,363. At $500 you finish with about $584,726. Exactly double, because nothing else changed.
Compare that to return. Squeezing an extra percentage point out of the market is difficult, uncertain, and usually comes with more risk. Raising your contribution is a decision you can make this afternoon.
Why early dollars outrank late ones
A dollar contributed in year one compounds for thirty years. A dollar contributed in year twenty five compounds for five. They are the same dollar to you and very different dollars to the calculation.
This is the practical argument for routing raises into savings before lifestyle absorbs them. The increase itself is modest. The thirty years attached to it are not.
Rate, not amount
Track contributions as a share of income rather than as a fixed figure. A fixed amount silently shrinks as a proportion every time you get a raise. A rate holds its ground.
Sources
- Figures are the future value of an annuity computed with monthly compounding at an assumed 7 percent annual return.
- The 7 percent assumption sits below the roughly 10 percent nominal long run S&P 500 average recorded by Aswath Damodaran at NYU Stern for 1928 to 2025, leaving room for inflation.
Open Forecast. Move the monthly amount and watch every bucket and the projection respond.
Open in Capital Allocation →