Salary compression is what happens when new hires enter at pay levels that match the current external market, while existing employees remain at the levels they were hired at one, two, or three years earlier. The market drifts up; internal pay doesn't drift with it; the gap between the two narrows or inverts.

It is not the result of any decision anyone made. It is what happens in the absence of a decision. Which is why it is often invisible until a regulator, an employee, or a works council surfaces it.

How compression builds

The pattern follows a recognisable shape in the data. A company hires a Senior at €60k in early 2024. In late 2024, the market for that role has moved to €65k. In mid-2025, recruiting a comparable Mid requires €58k — a hire from the level below, on a higher market reference.

The Senior, still at €60k, has not received a comparable raise. The Mid, hired at €58k, will likely cross €60k within 12 months as performance increments apply. The Senior now earns less than the Mid they onboarded.

T+0
Senior hired at €60k. Market rate at the time of hire. Position is well-calibrated.
T+12mo
Mid hired at €58k. Market for Mids has drifted up. The Senior, unchanged, is now €2k above the new Mid hire.
T+18mo
Mid receives performance increment. Now at €61k. Senior, still at €60k, is now compressed below the level they manage.
T+24mo
The Senior compares pay with the Mid. They learn — through the right to information, through a casual conversation, through a salary disclosure tool — that the inversion exists. The conversation that follows is not one HR controls.

The compression was built in a single decision sequence: hire the Senior at then-market, do not adjust internal pay annually, hire the Mid at then-current market. Each individual decision was defensible. The outcome was not designed.

Why this matters under the directive

Compression intersects with the PTD in three ways.

First, observed differences become harder to explain. The Senior earning less than the Mid is an observed difference within a category of equal work or work of equal value. Under Article 4, this difference requires an objective gender-neutral explanation. "We hired them at different times" is a factual statement, but the rationale that should ground it — annual market adjustment — is the missing piece.

Second, Article 7 requests become more pointed. An employee asking for comparator information now has a clear referent: the colleague they actually compare to in daily work. If that comparator is paid more despite being more junior, the company answers a more uncomfortable question.

Third, the joint pay assessment trigger (Article 10) fires on category-level gaps above 5%. Compression often manifests as a per-category gap that cannot be explained by tenure (Senior has more) or performance (the Mid is doing well, the Senior is too). The remaining explanation is "market timing" — which the directive views as an objective factor only if it is documented and applied consistently across genders.

Worth noting

Compression is gender-neutral in cause but not always in effect. Women are over-represented in cohorts that tend not to negotiate increments mid-tenure; men are over-represented in cohorts that re-enter the job market more often. The compression that develops over 24 months can show up as a gender pattern at the category level even though no specific hiring decision was gender-influenced.

How to detect it before the regulator does

Compression is observable in the company's own data. Three checks surface it:

Compare new-hire offer ranges to existing-team distributions. For each role band, plot the existing team's pay distribution and overlay the last 12 months of new-hire offers. Compression is present when new-hire offers cluster above or near the existing team's median.

Trace tenure vs pay correlation. Plot each employee's pay against their tenure within the company. A healthy distribution shows positive correlation: tenure rewards pay, all else equal. A compressed distribution shows flat or inverted correlation in some role bands.

Examine the offer-to-existing ratio per role. For every new offer, compare it to the existing-team P50 for the same role. A ratio consistently above 1.0 indicates ongoing compression-build.

What addressing it looks like

The directive does not prescribe how to fix compression — it requires that pay decisions be explainable. The practical response is a deliberate one:

  1. An annual market-adjustment process applied at the same cadence across all role bands. Compression is reduced when internal pay tracks external market within a defined band.
  2. Offer-range governance that pre-defines what counts as "market" before each hiring round, with documented criteria for above-range offers.
  3. Cohort comparison before each offer. Where the proposed offer sits relative to the existing team in the same role and level is a question worth answering before the offer is extended.
Compression is not a hiring problem. It is a pay-maintenance problem that surfaces at hiring.

Where the diagnostic starts

Detecting compression requires a defined role architecture and a clean payroll export — the same inputs the directive's reporting obligation requires. The two go together.

The ReadinessCheck™ surfaces whether the structural inputs are in place. It does not detect compression; it tells you whether the company is positioned to detect it.

Compression is observable

The data shows when it was built. If the categories exist.

ReadinessCheck™ takes about 20 minutes and requires no salary data. It produces an observational position view of where the company sits on category construction and pay-setting documentation — the inputs both reporting and compression detection depend on.

Start the ReadinessCheck →