Episode 4
The Measured Decision
She gets to measure one more number, and it turns out to be ice creams per hour. The first calculation with it explains day two in a single line — and shows why rewarding a metric is a bad idea.
The board’s answers nearly all landed on the same number: ice creams per hour.
That is the right pick, and the reason can be shown rather than asserted. Mira’s costs run on two clocks. The buy-in runs per ice cream. The wage runs per hour. Any number that is going to tell her something has to hold both clocks side by side.
“How many people were at the lake” doesn’t do that. Interesting figures are cheap; figures you can decide something with are rare. At work they get called A KPI is one of the handful of numbers you can actually decide something with — not the twenty that just look impressive. Sales per hour is a KPI; how many people were at the lake usually isn't. full card numbers, and they sit in dashboards next to twenty that aren’t.
The line
Every ice cream brings in €1 and costs €0.50 to buy. That leaves €0.50, which is her Contribution margin is what a single ice cream contributes toward fixed costs and profit after the cost of goods — at a €1 price and a €0.50 buy-in, that's €0.50 a unit. It's the number that decides whether a second seller is worth it. full card on every ice cream she sells.
An hour of classmate costs €5.
So the question is this: how many ice creams does a bought hour have to sell to pay for itself?
€5 divided by €0.50 an ice cream. Ten ice creams.
Ten an hour. Below that Mira is paying for the privilege; above it, she is earning. That is Break-even is the point where contribution margin exactly covers the wage — at €5 an hour in wages and €0.50 margin per ice cream, that's exactly 10 ice creams an hour. Below that she's losing money, above it she's earning. full card in its smallest possible form — not a concept, a division.
The line hangs on exactly two numbers. Raise the wage to €6 and it moves to twelve. Sell the ice cream at €1.20 and it drops to a little over seven.
The calculator shows the line per day: 100 ice creams over ten hours is the same ten an hour.
Day one, again
100 ice creams, ten hours. Ten an hour.
Her own average on the celebrated first day is precisely the line.
So day one was not a good day. It was an exactly paid one. That is why nothing was left in Episode 3 once she counted her own labor: an average of exactly ten leaves exactly zero.
Day two: 180 ice creams, twenty seller-hours. Nine an hour. One under the line. One missing ice cream is €0.50, and twenty hours at €0.50 is €10. Exactly the shortfall from Episode 3.
Price the bought hours on their own and it gets sharper still. They produced 80 extra ice creams, which is €40 of margin against €50 of wage. Eight an hour bought, against a line of ten.
One caveat belongs here, or Episode 3 was wasted: that arithmetic assumes day two would have produced 100 ice creams again without help. Nobody knows that.
Which is the point. The line is worth little as an explanation of yesterday and a great deal as an instrument for today: count, look at the clock, decide — before the evening rather than after it.
One more thing. When Mira works the stand herself, the wage moves from her left pocket to her right, and the bicycle fund gets both halves. For her own hours the line is a price tag rather than a rule: €5 is what an hour of ice cream selling costs her to buy. Under ten an hour, a bought hour is worth less than it costs.
What holds still and what grows
Now the negotiation from Episode 2 pays off, almost word for word.
Mira had offered commission: half the margin, €0.25 an ice cream. The classmate wanted €5 an hour.
On commission there is no line at all. Cost only happens when an ice cream crosses the table, and an empty afternoon costs nothing. On an hourly wage, ten hours are bought before the first ice cream is sold.
And a detail that gets lost constantly in real companies: fixed and variable are not properties of a cost, they are relationships. The hourly wage is fixed with respect to units sold and variable with respect to hours. Confuse the two and you buy hours as though they were ice cream.
The commission would also have delivered what Mira still doesn’t have. People paid per ice cream count their ice cream. The pay model would have been the measuring device.
Had the two sold the same amount — which nobody knows — the classmate’s commission on day two would have been 90 ice creams at €0.25: €22.50 instead of €50. Certainty had a price that day, and Mira paid it.
The cobras of Delhi
The colonial administration in Delhi had a snake problem and a reasonable idea: a bounty for every dead cobra handed in. The number of cobras handed in went up. The problem did not. Eventually someone noticed that people had started breeding cobras. When the program was shut down the animals were worthless, so they were released. There were more cobras at the end than at the start.
Honestly: the story is better documented as a story than as a record. The economist Horst Siebert gave it its name in 2001, and no one has yet produced a document out of colonial Delhi. It stays in circulation anyway, because everyone who hears it immediately has an example of their own.
The principle underneath doesn’t need snakes. Once a metric is rewarded, people optimize the metric rather than the goal. Economics calls it Goodhart’s law, after a 1975 paper by Charles Goodhart. The quotable version — “when a measure becomes a target, it ceases to be a good measure” — is actually the anthropologist Marilyn Strathern’s, written in 1997.
Mira’s cobra farm would be easy to build. She wants a high average? Then she works only the one busy hour in the afternoon: 20 ice creams, an average of 20 an hour, the best number of the summer. The bicycle fund gets €10. A full day averaging twelve sells 120 and puts in €60. The metric would be two thirds better and the tin would hold a sixth as much.
The bicycle costs €500, not 20 ice creams an hour.
Now turn the mirror around. What were you rewarded for most recently — and what did it actually set off? Not what it was supposed to set off.
Over to the board
Mira has a rule she didn’t have before: a bought hour pays from ten ice creams up. What she does not have is a place where she knows ten is available.
She does have a suspicion. Fifty meters along, at the meadow by the dock, there are more towels on the grass than on her stretch of the path.
She thinks the other spot sells better. How do you find out whether she’s right?
One day over there and a comparison with yesterday won’t do it — Episode 3 settled that. In Episode 5 she turns it into four days, and one rule that is harder to keep than it sounds.