Co-written by Claude Code Opus 5·Directed by Martin Hoshi Vognsen
Eight reproducible analyses of a single ordinary question — which car to buy — worked to the point where the answer stops depending on taste. Each note states its assumptions in one parameter block, sources what can be sourced, labels what cannot, and shows the mileage or price at which its own conclusion reverses.
What a car costs over its life, and what the contracts around it are worth.
Electric, petrol, diesel and plug-in hybrid in Denmark, 2026 — and the point at which the cheapest kilometre stops being the cheapest car. Separates marginal cost, price-free running cost at matched mileage, and full TCO, because they give different answers.
The bZ4X Touring and the e-Outback are the same hardware under near-identical warranty mechanisms, and one number apart. Prices the difference as an insurance payoff — degradation as a first-passage problem solved in closed form rather than simulated, calibrated two ways, with the verdict bracketed by claim severity.
Annual depreciation estimated per brand from used listings, as a log-price model in age with mileage held constant, plus a sparse new-price cross-check. Ends with a Solterra-vs-bZ4X case study on badge-engineered twins.
Totaløkonomi pr. år med alternativomkostning, holdeperiode og ekstra-km. Sammenligner privatleasing mod kontantkøb og lånefinansiering over en otteårig horisont, med afkastet af den bundne kapital prissat eksplicit.
One question where the answer is mechanical rather than financial.
Where the criteria are genuinely incommensurable, the honest tool is an explicit weighting: the priorities are written down and ranked before any car is scored, so a reader can disagree with the weights rather than with the conclusion.
Den generelle model: skalerer til vilkårligt mange biler, med otte prioriterede kriterier fra driftsikkerhed til fartbump. Manglende data håndteres eksplicit — et kriterium med for få oplysninger udelades og siges udeladt, frem for at blive gættet.
Billige, fabriksnye biler med automatgear, scoret på den samme model med et kriteriesæt tilpasset segmentet.
Samme model igen, denne gang for små fabriksnye elbiler, skåret ned til tre vægtede kriterier: samlet økonomi, driftsikkerhed og personsikkerhed.
A note on the pages. Each note is a single self-contained HTML file with its figures embedded, so it works offline and will still open in a decade. That makes them large — 2 to 6 MB each — and slow on a phone connection.
A note on the numbers. These are working notes about one purchase decision in Denmark in 2026, not advice. Several of the most load-bearing figures are labelled as estimates in the notes themselves; the raw used-car listings behind the depreciation work are not redistributed. Prices, taxes and specifications were correct on the retrieval dates given at each point of use.