Number Drift: When Your Number Changes

Every week, about forty sleepers write to tell us that their Number has changed. Most of them sound worried. A few sound betrayed. One wrote simply, “Fifty-two was my whole personality.”

I want to say clearly, at the start: Number Drift is normal. It is not a fault in your pillow, your Protocol or you. Your Number describes the relationship between your neck and your stack on the nights you measured it. Relationships change.

How common is it?

Among sleepers certified for at least two years, about 14% have recorded a drift of one layer or more. About 3% have drifted by five or more. The largest drift we have certified is 19 layers, in a sleeper who moved from a firm mattress to a very soft one and, she tells us, “sank into a different person”.

The median drift is two layers. Most sleepers who drift move back within a year.

What causes it

We have identified six common causes. They account for about nine drifts in ten.

1. A new mattress. The most common cause by far. A softer mattress usually raises your Number. A firmer one usually lowers it.
2. A new sleep position. Side sleepers who become back sleepers typically drift down by six to ten layers.
3. A new partner. Partners change how much of the bed you have, which changes how you lie on it.
4. A change in your shoulders. Swimming, climbing, rowing and carrying small children all count.
5. A move. A new bedroom brings a new temperature and a new humidity, and the Thermal Stratum responds to both.
6. Time. Necks change slowly. Sometimes a Number simply moves with them.

The remaining drifts we cannot explain. We record them anyway. One sleeper’s Number rose by three layers every winter for four years and fell by three every spring. We have stopped calling this an anomaly and started calling it a pattern.

What to do

If you think your Number has drifted, please do not guess. Guessing is how people end up with eleven pillows.

1. Return to your last certified Number for three nights. Confirm that the discomfort is real and not a single bad night.
2. If it persists, open your Sleep Journal to a new page. Write the date and the words “Drift Check”.
3. Adjust by one layer each morning, following the usual Layer Removal Etiquette. Add layers from the Caddy if you need to go up.
4. When you wake without discomfort for three consecutive nights at the same count, you have met the Triple Quiet again. Your new Number is certified.
5. Send us a photograph of the Journal page. We will re-engrave your Number Card at no charge.

This is why we recommend keeping every removed layer, in order, in the Caddy. A sleeper who drifts upward and has given their layers away must reorder them. We will always help. But it is easier if Layer 53 is in the drawer.

A word on identity

Many sleepers become attached to their Number. They order the mug. They tell their book club. When the Number moves, it can feel like losing something.

I would gently suggest that your Number was never a fixed fact about you. It was a measurement, taken with care, of how you were sleeping at the time. A new measurement is not a contradiction. It is just more information.

I would also note that we re-engrave the mug, too. That costs $12.