field note · concept
every churn tool counts dead bodies. here is why that is the wrong unit of measure.
readout · one population, two units of measure
A churn number is a body count. It tells you how many accounts were alive at the start of the period and how many are alive at the end, and it calls the difference insight. The arithmetic is honest enough. The unit is not. Counting who has left is the one measurement guaranteed to arrive after the only moment you could have done something about it. There is a better unit hiding in the same population, available earlier, in finer grain, and in the living.
presence is binary, and it is retrospective
Every churn tool measures presence: active or cancelled, retained or lost, one or zero. It is a coarse tally of state flags; a binary marker can only flip after a decision has fully resolved. By construction the metric updates on exit. You are counting bodies as they fall, which means the number is always a record of what has already happened. And it is coarse in the way any headcount is coarse: a customer is a one until the instant they are a zero, with nothing in between, even though the entire story you care about is what happened in between.
density is continuous, and it is present-tense
Inside the population that is still fully present, every flag still reading one, there is structure the flag cannot show. Some segments are saturated with friction and some are not. The same headcount can sit on top of completely different internal pressure. Density is that pressure made measurable: the local concentration of unresolved friction per unit of population, read in real time among the people who have not moved. It represents a continuous scalar value that spikes long before any binary flag flips. Presence cannot register it, because presence only registers the flip.
The dead bodies are the least informative members of the population. Their decision is made, and it is the one you can no longer change.
why the dead are the wrong place to look
Counting departures has a survivorship problem in reverse. The metric describes the people who already left and stays silent on the pressure bearing down on the people who stayed, and the people who stayed are the entire addressable population. The information you can act on lives in the living. A churn count is a symptom printed after the fact. Density is the state that produced it, readable while it is still forming. Epidemiology settled this argument long ago: mapping localized virus prevalence vectors outperforms a historical log of fatalities. You can map an outbreak by counting the dead, but that count only tells you where the disease has been. What predicts the next wave is transmission density in the people who are still well.
measuring the right unit
Density is measurable because a population leaves a continuous record of its friction before it acts, in what it says rather than in what it has cancelled. Cluster that record into a friction graph, weight it, and you derive a continuous scalar field; a topological map of potential energy where segments naturally slide down the gradient of compounding friction. The at-risk cohort stops being a retrospective headcount of exits and becomes a geographically visible region of high density, mapped before it ever converts. And once the unit is density, the move you were about to make becomes testable. Apply the named stress, watch where density spikes past the threshold, and read the answer off the living population instead of waiting to autopsy it.
Presence tells you how many bodies have fallen. It is precise, it is honest, and it is the wrong question. Measure the density of friction in the part of the crowd still standing, while standing is a choice they are still making.