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The demonstration, UK railcards, is a bit odd. I thought they were sharing too much information, date of birth when only something like "under 18" would be needed. But these railcards have several different age-based options. What is the point of this age discrimination, surely you take up one seat on a train regardless of your age?

Per https://www.railcard.co.uk/

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Railcards in the UK have a complicated history, but essentially there's a sliding scale of discount you can get up to the age of 30, in order to encourage more young people to use the rail network. You get more discount under 18, some between 18 and 25 for one price, and some between 25 and 30 for another price.

Additionally, the way the discounts work is that you buy a pass that lasts for a period of time. That then needs to work with your current age. i.e. you can't buy 2 years of discount for under 30s at 29, you can only buy 1 year, so they need to share your age and I think possibly in some cases, date of birth.

But then you start getting a discount again when you are over 60, or a veteran of the armed forces? The 30-60 age group is hit hard!

Which age tranche is the richest?

Its like "people in your age range are richer than average, so we are going to charge you extra."

I prefer to frame it more like this: "People in your age range drive less or cannot legally do so and as such have few other options for transit, so we'll give you a discount. Also, the negative externalities of rail travel are far lower than other modes of transit so we should encourage as many people as possible to use it. When a frequent young user of rail transit grows out of the lower price bracket, they will likely continue to use the service to help keep it affordable for all."

Also, <25 and >60 are probably much less likely to be using rail to commute to paying jobs. Additionally most of the Railcards are scoped to only off-peak travel, which again focuses on leisure/family rather than work.

It's a blunt tool, but it's not terrible.

I suppose it would almost work for me, I had my highest income in my early 40s, but now I'm in my 50s and my income is quite low.

Over 60's

I'm not familiar with the specific situation in the UK, but age-based discounts can support many policy goals.

Maybe you want teenagers to be more independent, instead of relying too much on their parents for transportation needs. Maybe you want young adults get used to using public transit instead of driving everywhere, which can lower infrastructure costs in a densely populated country. Maybe you want to encourage retirees to get out and participate in the society, instead of sitting alone at home. Or maybe you want to encourage the use of public transit outside peak hours, which could reduce the overall need for subsidies.

Simple systems, such as age-based categories, often work well enough. Targeted subsidies can be more efficient in principle. But that assumes that regulators manage to target them properly and have the regulations implemented in software correctly and in time. All of those often fail. And even when they are successful, they may cost more than you save with better targeting. Not to mention the opportunity costs: when regulators focus on one thing, they can't work on another.

The Railcard website you linked is pretty clear.

> For those aged 16-25, save 1/3 off rail fares for days out, seeing family and friends and even festivals!

> For those aged 60 and over, save 1/3 off rail fares for days out, holidays, seeing family and friends, and theatre trips!

So, provide proof of age via ID and get a discount. It's very common on public transit for the young and elderly to get a discount.

and the 26-30 Railcard, and the Children aged 5 to 15, and the for those aged 16 or 17, it just seems weird to have all these age-restricted options for exactly the same product (a seat on a train.)

Call it woke or socialism, but perhaps it's within a society's interest to make travel affordable for people who don't necessarily have access to other modes of transit. It's the difference between equality and equity.

I'm not sure that age is the biggest factor in wealth inequality. I could be wrong, but there are plenty of rich kids and poor middle aged.

Proper ZK off of that would be it would simply provide which of those age ranges you're in, not your actual date of birth.

Yeah, but what if the company has 36,500 age based discount tiers (or has heard of binary search)?

I don’t see how revealing the result of a less than comparison can be considered zero knowledge, but then I also don’t understand the difference between Google exchanging actionable confidential facts about you for money and them selling your personal information, so what do I know?

Well, a compromise would be to simply provide the user's age in years, as opposed to their date of birth. Effectively a 365-day resolution instead of 1-day.

Demand they check every day, sell partial year passes, or require ID when buying alcohol, and correlate year in ages to CCTV footage.

This class of scheme flat out doesn't work.

ZK biometric telomere measurements coming soon to a turnstile near you!

Age is a proxy for money. You want to set the price for optimum profit (assuming the rail company isn’t controlled by the government and implements social measures), so you want to charge every group of people the amount where (number of costumers)*(profit per customer) is maximized. If you would price every group the same fare, some people wouldn’t get a ticket and you would lose customers. It makes sense to charge those users less, but try to keep the profit of other groups higher by not reducing their fare.

If they want to go that way, why even use a proxy? Just demand annual income instead of age, and make the price a fixed fraction of the income.

Because it’s much harder to verify annual income than just checking the birthday on the ID, I guess.

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