EXPERIMENTS · BUILT
How often does a newcomer last a day?
Stories enter the top 25 from nowhere every day or so. The record keeps count of how many are still there a day later.
- Question
- Of the stories that enter the top 25 from nowhere, how many are still there a day later?
- Method
- A newcomer is a top-25 story that was not in the previous run's top 100. Follow it forward four runs, through any change of cluster id, and record whether it is still in the top 25. Grouped by the rank it entered at. A base rate from the record, not a forecast.
- Result
- 16 of 23 newcomers were still in the top 25 a day later (70%); about 0.64 a run enter from outside the top 100.
- Decision
- Record only. No story page shows a probability. The rate by entry band is not read until each band has 30 newcomers.
How it was measured
Every run ranks every story. A newcomer is a story in the top 25 that was not in the previous run's top 100, or did not exist. It is followed forward four runs, about a day, through any change in its cluster's id, and counted as held if it is still in the top 25 then. Newcomers whose day is not over are pending.
This is a record of what happened to stories like this one, kept as the runs accrue. It is not a forecast for any story, and no story page shows one.
The numbers
16 / 23newcomers still in the top 25 a day later (49–84%)
0.64newcomers a run, over 37 runs
0pending: their day is not over
By the rank they entered at
| Entered at | Newcomers | Held a day | 95% interval |
|---|---|---|---|
| #1-5 | 0 | – | |
| #6-15 | 9 | 8 (89%) | 56–98% too few |
| #16-25 | 14 | 8 (57%) | 33–79% too few |
A band is not read until it holds 30 newcomers; until then its interval is too wide to tell bands apart.
Limits
- Snapshots of every run exist from 23 Sep 2026; about one story a run enters from outside the top 100, so the rate fills slowly.
- The record has 2 outages (runs more than nine hours apart). The first run after one counts no newcomers, and 1 newcomer whose day ran into one is left out.
- "Held" follows a story through changes of cluster id by shared articles. A story that splits or merges can be counted as gone when a reader would say it continued.
- What keeps a story in the top 25 includes the rule itself: see how much of What Moved is the rule.