Five stages, each one good. Chain them, then choose where the humans look. Watch a pipeline of individually strong stages deliver a mediocre corpus, and see why the errors land on exactly the documents that matter.
The pipeline · five stages
Good stages, compounding losses
Each stage keeps most documents right. But accuracy multiplies through the chain, so five strong stages still hand you a corpus with a real error rate. Drag any stage.
The toggle. Switch from "spread evenly" to "cluster on bad documents" and the headline accuracy barely moves, yet the errors pile onto the worst 5% of the corpus. The average hides the harm.
The review gate · where humans look
Buy back fidelity per hour
Put a human-review gate after one stage, and route the lowest-quality documents to it first. The same review budget buys back far more when the errors are clustered.
Review budget5%
no reviewworst 20% reviewed
Route by quality, not at random. The budget reviews the worst documents first: all of the awful band, then into the degraded band. In clustered mode that tail carries most of the errors, so each review-hour is worth several times more.
The numbers · expected values over 10,000 documents
Readouts
End-to-end intact77.4%before any review
Documents with an error2,262at least one, of 10,000
Errors on the worst 5%5.0%share carried by the awful band
Fixed per review-hour6.8errors caught per hour
End-to-end after review78.5%intact once review fixes its queue
The corpus, worst on the right
Each cell is 100 documents, ordered clean → degraded → awful. Brighter red means more expected error. The bracket shows the tail sent to human review.
Expected error densityRouted to review
The stage waterfall
One hundred percent of documents enter. Each bar is the share still fully intact after that stage; the red slice above it is the loss that stage adds.
Still intactLost at this stage
All data is synthetic and the model is illustrative. This is a teaching model of a generic pipeline, not a description of how any live system works.
Paired with the article Parsing the Paper Mountain.