What is the probability of someone sharing my name & date of birth?

[Welshguy]

Do you understand that this drastically changes your original question? For one thing, you used as your universe the entire adult population of the UK. That universe is entirely irrelevant unless every adult in the UK is an online punter with an admitted gambling addiction. I'd venture a guess that the relevant universe is one or two orders of magnitude smaller, which completely alters the math.

It is of course still true that if there are 25 David Smiths registered as gambling addicts, the probability that at least two will have been born on the same day of the same month will be in excess of 50%. (This is true even though tkhunny is correct that we live in a deterministic world so that it is never strictly true that human behavior is perfectly random.) But once you add year of birth the probabilty that 25 almost random adults will have been born on the same day of the same month of the same year becomes virtually zero.

The real problem, as the wise S. Khan has pointed out, is that addicts will lie about their birthdays if the truth will prevent them from gambling. DOB is absolutely useless if it cannot be verified. The same is true of name. I have experience in the US with the so-called OFAC list, a government list of the names of suspected terrorists and drug smugglers that banks must check before sending money out of the country. The rate of false positives is negligibly different from 100% because terrorists and drug smugglers tend not to be excessively truthful with the authorities. Anyone can lie about his or her birthday.

Because gambling addicts have less incentive and far fewer means to evade detection than terrorists and drug smugglers, what is likely to be more effective than DOB is payment address: gamblers want to be paid when they win, and the bookies want to be paid when the gamblers lose. No one in the gambling business cares about birthdays; everyone cares about payment.

Thanks for getting back to me. It is irrelevant whether or not they are gambling addicts. The system has to be the same for every customer of the company.

In the UK, you have to by law use either passport or driving licence to open a gambling account online. So you can't open an account in a false name/DOB (unless you use someone else's ID, but that is a different matter). As the passport only contains name & DOB, this is all that they can go on sometimes. It is easy to change the address/phone number. What the companies say is that there would be too many false positives just using name & DOB.

Now if we go to court and they provide evidence that they have thousands of false positives every day, then they have a valid argument. But even if it is 100/day, a company making hundreds of millions of pounds per year profit could quite easily employ someone to manually check the IDs of any matches. In fact they have a legal requirement to do so.

I was purely using the entire population of the UK as a worst case scenario. It is impossible to get exact numbers as we have no way of knowing details of the customers of these companies. All we need is evidence that there is reasonable doubt about what they are saying.

Thanks again!

 

[Welshguy]

Every time you talk you change your story. You leave out facts, etc. I have no interest in helping liars.

That's a bit harsh!! I've not intentionally changed my story, or left out any facts. It's just difficult trying to convey what I'm trying to achieve. It's a complicated system!

Sorry if that's the way you feel.

Cheers

 

[JeffM]

That's a bit harsh!! I've not intentionally changed my story, or left out any facts. It's just difficult trying to convey what I'm trying to achieve. It's a complicated system!

Sorry if that's the way you feel.

Cheers

You are right. I shall delete my post.

I have experience working with lists of prohibited people. In my case, lists compiled by the US government, presumably with help from other governments. Over many years, we never had a true hit. Several hundred false positives per year. The problem with trying to address this through probability theory is that what is being observed is not at all random. The people who do not want to be on such lists take pains to avoid detection.

I also have experience with "know your customer" regulations. If they are serious, they are onerous because they apply to every customer, not just those who are of interest. If they are not serious, they end up being ineffective.

The issue is about balancing social costs. How much would serious "know your customer" regulations cost and end up being imposed on customers who have no problem versus the social costs of people who suffer from gambling addiction. You cannot solve such problems by playing around with probability theory. And it is silly to think that profit-making businesses will simply absorb extra costs out of profits; prices will increase to impose those costs on consumers.

I am sorry about getting so exasperated. I have just had too many experiences where people want magic bullets and do not care very much whether they make any sense.

EDIT: I have little good to say about gambling. But the US has tried to prohibit or impede pleasurable activities on the frequently legitimate grounds that those activities are objectively bad for people. These efforts have frequently turned out to be both quite ineffective and quite adverse in their overall social effects, e.g. Prohibition. For every problem, there is an easy answer that is wrong.