What If: We Built a Time Machine, but Only for Your Portfolio
Macropoiesis now has virtual portfolios. Copy your real one, go back in time, make the trades you swear you almost made, and let the replay engine calculate exactly how right you would have been. This is a feature announcement. It is also a public-health warning.
Every investor owns two portfolios.
There is the real one, containing the trades actually made, and there is the imaginary one, where you bought NVDA in October 2022, sold everything else at exactly the right moment, and have been quietly outperforming Warren Buffett ever since.
The imaginary portfolio has always had one decisive advantage: nobody could check the math.
We are pleased to announce that this era is over.
What If is live on Macropoiesis.
It turns the imaginary portfolio into a testable counterfactual. Clone an existing portfolio or start from nothing, insert trades at historical dates, and replay what would actually have happened from that point onward using historical prices.
In other words, hindsight now has unit tests.
It is not technically a time machine, because physicists remain disappointingly uncooperative. But for a portfolio, it is close enough.
How it works
You start a scenario in one of two ways.
Blank, if you prefer to begin history with the benefit of knowing how it ends. You get an empty portfolio and several years of hindsight at your disposal.
Copy of a real portfolio, if you want something more surgical.
This clones your actual positions into a sandbox where you can finally perform the trade you have spent six months explaining you should have made earlier.
Sell the stock before the drop. Buy the one before the rally. Reduce the position you now insist was "obviously too large."
The copied portfolio gives the replay engine a common starting point, so the scenario can be compared directly with what actually happened.
When the two curves diverge on the chart, that gap has a precise technical name:
the cost of being you.
Then you add trades.
Pick a ticker. Pick a date. The form automatically fills in the historical closing price for that day.
Buy in the past. Sell in the past.
The replay engine reconstructs the equity curve day by day, as though you had actually made the trades.
The useful part is not that you can rewrite history.
The useful part is that history gets to answer back.
The charts do not respect your feelings
Once a scenario exists, the visualizations appear. They have made no commitment to preserving your self-esteem.
A per-trade waterfall decomposes the result trade by trade.
"The market" is no longer an admissible explanation. The chart has names and dates.
A drawdown chart shows every period in which the scenario falls below its previous high-water mark. The industry, with unusual honesty, calls this an underwater curve.
Some scenarios spend so much time underwater they qualify as marine life.
A monthly return calendar shows exactly when the alternate version of you prospered, struggled, or discovered that knowing the future in general is considerably easier than knowing what to do on a particular Tuesday.
It is also useful for identifying the particular month your supposedly wiser alternate self would have panicked in.
A before/after score gauge evaluates the portfolio using the same risk and performance criteria before and after your changes.
Sometimes the alternate portfolio improves.
Sometimes it produces the cruelest verdict available from modern software:
your brilliant idea made the number go down.
And then there is the projection.
One button runs a Monte Carlo simulation across two thousand possible futures while preserving the estimated statistical relationships between the assets.
Two thousand.
You have been arguing about one future.
The machine disagrees with you in bulk.
The fine print, which is honestly the funniest part
A historical simulation becomes very impressive very quickly if you allow it to quietly make things up.
We decided not to.
That produces a few rules.
You cannot have a return before you have invested.
Until capital is actually deployed, return is not zero. It is undefined.
Zero percent would claim that an investment existed and neither gained nor lost. Before the first investment, there is simply nothing to measure.
In the interface, that appears as null: the software equivalent of "no comment."
Impossible trades are refused, out loud.
If a trade cannot be placed against available historical data, the engine does not quietly improvise a convenient price.
It skips the trade and tells you.
The time machine has a bouncer.
Foreign currencies are not silently converted.
A position quoted in EUR and one quoted in USD are replayed in their native quoted values. The system does not invent an exchange-rate conversion and then present the result as though the comparison were exact.
Your fantasy may be multi-currency.
At least the disclosure is honest.
This is a fairly simple principle: when the data cannot support precision, the interface should not manufacture it.
Finance already contains enough imaginary certainty without software volunteering to add more.
The disclaimer we mean sincerely
Nothing in What If touches your real holdings.
Not the trades. Not the deletions. Not the scenario where you sell everything and go all-in on one semiconductor company because you have "done the research."
Your actual portfolio is fully insulated from your imagination, which is a service some investors probably needed before the invention of electricity.
The scenario remains exactly what it should be: a counterfactual.
You can change it, destroy it, rebuild it, or create several competing versions of your personal financial history.
Reality remains stubbornly read-only.
Hindsight, now with numbers
Investment hindsight is usually expressed in sentences.
I knew it would recover.
I almost bought there.
I would have sold before the drop.
Sentences are wonderfully forgiving things.
They have no position size. No execution date. No opportunity cost. Usually no drawdown. And they improve noticeably with age.
What If gives them all four.
It turns "I should have" into an actual trade, the trade into an equity curve, and the equity curve into something that can be compared with reality.
Sometimes the numbers confirm the story.
Sometimes they perform a small public service by killing it.
So go ahead.
Build the portfolio where you were right about everything.
Replay it.
Check the waterfall.
Inspect the underwater curve.
Compare it with what actually happened.
Then close the tab quietly, and never tell anyone what the comparison chart said.
What If is available now at /what-if for logged-in users. Side effects may include humility.