One question, three tools
Does a stable manager win more trophies? Sir Alex Ferguson spent 27 seasons at Manchester United and turned the club into a trophy machine. José Mourinho won almost everywhere he went and rarely stayed longer than three seasons. This site started from the wish to see that difference, not just read about it. The question never changed. The tools did, and how long it took to answer it changed with them.
Photoshop: months of evenings
The first version was a single image, made by hand in Photoshop in January 2022. Every season a block, every block coloured by how long the manager had been in charge. The data came from a spreadsheet that I filled myself, with only a little help from AI. Working out who was the longest-serving manager in each season, decades back, took months of evenings. I was proud of it and posted it on Reddit's r/dataisbeautiful. The reactions were disappointing enough to put the project away.
The idea stayed, and it became my personal test for AI. With every new chatbot I asked the same thing: give me a complete list of Ajax managers. For a long time the answers were full of invented names, like in this conversation. A simple search was already too much.
Gemini: copy, paste, repeat
Then Gemini passed the test, and the project came back to life as a website. Gemini wrote the code, I copied it into HTML files on GitHub, and when something broke I pasted the error back into the chat. That is how the Firestore database, the data dashboard and the automated searches for missing data were built. It worked, eventually, but with a lot of blood and tears. Chats filled up, answers looped back to old questions, and I retyped the ground rules of the project more times than I can count:
"We communicate in Dutch, but the visualization is in English. Always provide the full code in the canvas without placeholders. Be professional, don't apologize, don't call my ideas brilliant, never say something is 'final', and always ask me before you code."
The result was a working site, but not the one I had in my head. That version is still online as an archive (v0.9).
Claude: two days
The last step took two days. On top of the existing database and dashboard, Claude (Opus 5.5) rebuilt the site from the ground up. The story of Ferguson and Mourinho now opens the site step by step, before you explore the data yourself. Seasons with more than one manager, interims included, are shown with red stripes, one stripe per manager. More than two thousand seasons were checked against Wikipedia in six languages, and the cases where sources disagreed ended up in the dashboard, where I can settle them with a tick. Missing manager photos were added from Wikimedia Commons, with their makers credited on a separate page.
I did not write that code, just like I did not write the Gemini code. The difference is that I no longer had to carry it from one window to another. I described what I wanted, checked what came back and corrected what was wrong. That is also the real story behind this project: the question stayed the same from the first Photoshop file to this version, and the time needed to answer it properly went from months to days.
How the data was collected and which choices were made along the way is explained on the Data Methodology page. Spotted a mistake? Use Report an error at the bottom of every page.