柏林有十六个月时间换新的黄信封，结果两个星期就用完，该进监狱的人留在了家里

Start with the outcome, because the outcome alone is strange enough.

In Berlin, Germany, a group of people had already been sentenced by a court to prison.

But they did not go. They stayed at home.

They had not run, and nobody was helping them.

Berlin could not get them into prison for one reason only: there were no envelopes.

That sentence is literally true, not a joke.

In Germany, some letters cannot simply be put in an ordinary envelope and posted.

Court judgments, notices, and the letter telling a person which day to report to prison all fall into that category.

Those letters have to go into a particular yellow envelope.

The yellow envelope is itself a procedural step.

In law it establishes one thing: this letter has been formally served.

The recipient cannot claim they never got it.

So the whole path is rigid.

With no yellow envelope, the letter cannot be sent.

If the letter cannot be sent, the person does not know which day they are supposed to go.

If the person does not know, they will not go.

It started with a very small change.

At the end of March last year, the German department responsible for justice changed what these envelopes look like.

The new envelope needed one extra tick box.

That was the whole change.

They notified everyone at the beginning of April, and they also allowed time.

The old envelopes could be used right up to the thirty-first of July this year.

From the notice to the final day, that is roughly sixteen months.

For switching an envelope, sixteen months is a very long time.

And Berlin did prepare.

Before the new rule took effect on the first of August, the new envelopes had been bought.

That part they got right.

The problem came at the next step.

The new envelopes they had bought ran out in two weeks.

Because the quantity actually needed was far higher than they had calculated.

When you run out you reorder — that is normal.

But this time they could not get any.

The manufacturer had none in stock either, and new orders had a long queue.

So Berlin ended up looking very strange indeed.

The court had passed sentence.

Beds in the prison sat empty.

The staff were all at work.

The only thing stuck was the letter telling the person to report — it could not get out the door.

A spokesman in Berlin said afterwards: this was only a short-term supply shortage.

They did manage to buy some more after that.

But the staff inside said: it still is not enough.

So how many people stayed home because of this?

Nobody knows.

Because nobody counted.

Here is what is genuinely interesting about this.

Take the system apart and you cannot find a single broken piece.

The law is sound, the judgment is clear, the prison has space, and the people are all at work.

The only thing it lacked was a paper bag worth a few cents.

The more formal a process is, the less any one of its steps can be replaced by something else.

The yellow envelope works precisely because no other envelope counts.

And the very thing that makes it work is what stopped the whole path dead the day it ran out.

Sixteen months of lead time, punched straight through by two weeks of actual consumption.

What was miscalculated was their own usage; the time was in fact plenty.

If someone gave you sixteen months to do one very simple thing, in which month would you start?