Learn · Research notes
Why timing the same paycheck failed
We tested skip/boost and pot-style DCA timing against blind weekly and monthly DCA. Honest results did not clear a shippable bar — invent-cash and contribution-path effects were the usual fake wins.
Direct answer
Timing when you deploy the same monthly savings did not reliably beat blind DCA after honest accounting. Apparent wins often came from inventing cash or measuring wealth the wrong way.
The product idea that sounded right
If you already invest every week or month, maybe a signal can tell you to skip, buy normal, or boost — same capital over the year, better path.
That is emotionally appealing. It is also easy to backtest badly.
How we broke our own illusions
Early charts looked great until we forced honest rules:
- No invent-cash. You cannot “skip” forever and then magically have a pile larger than the paycheck allowed.
- True TWR. `(final wealth / first contribution)^(1/T)` is forbidden on a DCA path. It confuses growth of capital with growth of deposits.
- Same annual dollars. Adaptive sizing that quietly spends more in good years is not a free lunch.
After those locks, pot-style and fib/momentum timing books collapsed toward ≈ blind DCA. The “smart” line was mostly a storytelling artifact.
What that means for S&P 500 DCA
If you searched for an S&P 500 DCA calculator hoping for a timing overlay, the research answer is boring:
Put the same amount in on a schedule. Weekly vs monthly is a small cadence choice, not a strategy. See weekly vs monthly DCA and the S&P 500 DCA calculator.
Related reading
Frequently asked questions
- Why timing the same paycheck failed?
- Timing when you deploy the same monthly savings did not reliably beat blind DCA after honest accounting. Apparent wins often came from inventing cash or measuring wealth the wrong way.
- Do you sell a trading strategy based on this research?
- No. These pages document what we tested and why we do not sell a paid allocator. Use the free S&P 500 DCA calculators instead.
Run the numbers on real history
Guides are cheap. Seeing a monthly habit on published S&P 500 prices is the point.