It would be immoral to disadvantage one nationality over another. But we also cannot disadvantage one age group over another. Or one gender over another. Or one hair colour over another. Or one brand of car over another.
So if we update this statement:
> Two people who are identical except for any set of properties face the same probability of a false positive.
With that new constraint, I don't believe it is possible to construct a model which outperforms a data-less coin flip.
We tend to distinguish between ascribed and achieved characteristics. It is considered to be unethical to discriminate upon things a person has no control over, such as their nationality, gender, age or natural hair color.
However, things like a car brand are entirely dependent on one's own actions, and if there's a meaningful statistically significant correlation owning a Maserati and fraudulently applying for welfare, I'm not entirely sure it would be unethical to consider such factor.
And it also depends on what a false positive means for a person in question. Fairness (like most things social) is not binary, and while outright rejections can be very unfair, additional scrutiny can be less so, even though still not fair (causing prolonged times and extra stress). If things are working normally, I believe there's a sort of (ever-changing, of course, as times and circumstances evolve) an unspoken social agreement on what's the balance between fairness and abuse that can be afforded.
Nationality and natural hair color I understand, but age and gender? A lot of behaviors are not evenly distributed. Riots after a football match? You're unlikely to find a lot of elderly women (and men, but especially women) involved. Someone is fattening a child? That elderly women you've excluded for riots suddenly becomes a prime suspect.
> things like a car brand are entirely dependent on one's own actions
If you assume perfect free will, sure. But do you?
That’s true. But the idea is that feeding it to a system as an input could be considered unethical, as one cannot control their age. Even though there’s a valid correlation.
> If you assume perfect free will, sure. But do you?
I’m not. If this matters, I’m actually currently persuaded that free will doesn’t exist. Which doesn’t change that if one buys a car, its make is typically all their decision. Whenever such decision is coming from them having a free will or entirely determined by antecedent causes doesn’t really matter for purposes of fraud detection (or maybe I fail to see how it does).
I mean, we don’t need to care why people do things (at all, in general) - it matters for how we should act upon detection, but not for detecting itself. And, as I understand it, we know we don’t want to cause unfair pressure on groups defined by factors they cannot change. Because when we did that it consistently contributed to various undesirable consequences. E.g. discrimination and stereotypes against women or men, or prejudice against younger or elder people didn’t do us any well.
To take a few examples, looking at employment characteristics will have a strong relationship with gender, generally creating greater false positives for women. Similarly, academic success will have greater false positives for men. Where a person choose to live will proxy heavily towards social economic factors, which in turn has gender as a major factor.
Welfare fraud in itself also has differences between men and women. The sums tend to be higher for men. Women in turn dominate the users of the welfare system. Women and men also tend to receive welfare at different time in their life. It possible even that car brand has a correlation with gender which then would act as a proxy.
In terms of defining fairness, I do find it interesting that the Analogue Process gave men a beneficial advantage, while both the initial and the reweighed model are the opposite and give women an even bigger beneficial advantage. The change in bias against men created by using the detection algorithms is actually about the same size as the change in bias against non-dutch nationality between initial model and the reweighed one.
One can't change one's race, but changing marital status is possible.
Where it gets tricky is things like physical fitness or social groups...
