What it measures
This score will tell you whether or not, on average, you tend to pay men more (compared to their "market") than women. In other words, this help you check whether or not you replicate, within your own company, the market reality that at equal role/seniority level, men are on average paid more than women.
While the Pay gap score helps you identify potential gaps within your own company, comparing men and women within the same roles, the Market fairness score allows you to compare each of your employee to the outside market they belong to (ie. what people with the same role are getting paid elsewhere).
Therefore it can be computed for companies of any size, because unlike the Pay gap score it does not require you to have men and women on the exact same roles.
Methodology
To understand this score, you need to fully understand the concept of percentiles. If that is the case, the calculation method is pretty simple:
We compute the Average Market Positioning (expressed as a percentile) of men compared to the outside market (based on their role, seniority level and location) and women (same criteria).
We compute the difference between both Average Market Positionings.
Starting at a 100% score, looking at the difference mentioned above, any % point in favor of men removes 10% of your score. Any % point in favor of women removes 5% of your score.
Example
Let's look at multiple examples of Average Market Positionings gaps and the resulting scores
Average Market Positioning - Men | Average Market Positioning - Women | Difference | Market Fairness Score |
56% | 50% | 6% favouring men | 40% |
43% | 40% | 3% favouring men | 70% |
82% | 85% | 3% favouring women | 85% |