Why Do We Always Seem to Run Into People Abroad?
We spoke to a coincidence expert to find out.
It’s a small world coincidence that makes you feel like a main character, probably because it often happens in vacation-style romcoms like Forgetting Sarah Marshall, Just Go With It, and even Emily in Paris: You’re thousands of miles from home, in a city you’ve never visited before, and you run into someone you know. If you’re a frequent traveler, it’s likely a serendipitous encounter of this kind has happened to you at least once in your lifetime. Reddit, for one, is teeming with accounts of people running into childhood friends, coworkers, and exes while abroad, or meeting a stranger on vacation and then reuniting with them years later.
So why does this happen? The obvious answer might be: Our travel decisions are influenced by our social network. How random is it, really, that you ran into another Millennial you know in the ever-so-trendy Mexico City, during the dry season? Maybe even the same one you bumped into in Iceland back in 2015? But that’s not the only factor. Despite feeling impossibly magical, there is real math behind the likelihood of these encounters, so we spoke to David J. Hand, British statistician and author of The Improbability Principle: Why Coincidences, Miracles, and Rare Events Happen Every Day, to help us break the odds down.
Thrillist: What is the likelihood of running into someone you know while abroad?
David Hand: I can’t give you a single figure which will cover everyone and all circumstances— like “on average every fifth time you go abroad you will bump into someone you know.” But perhaps we can try to get a ballpark figure—a rough calculation given in the next couple of paragraphs to suggest you might expect to run into someone you know about once every five years or so.
However, it will depend on all sorts of things, such as how many people you know, how often you go, and how long you spend abroad; whether you go somewhere people you know are also likely to go; whether you only go abroad in the school holidays, etc. Also, it should not be based solely on the people you happen to meet accidentally. After all, if you saw someone you knew on the other side of a crowded station concourse, you might well go over to greet them. So we really want to know: What is the chance of you and someone you know being in the same place at the same time when you travel abroad?
Suppose you “know” 200 people (there is some evidence suggesting that this is the right order of magnitude—you certainly know more than 10 and less than 1000). Suppose also that there are some 100 destinations you and each of the people you know might randomly choose from. This number will clearly depend on the individual—conservative types might simply go to the same place for an annual holiday, while adventurous types might stick a pin in the world map at random—but say 100 on average.
And say that you and each of the people you know stay a week each year, randomly chosen from the year. Again, depending on the people, that could be way off the mark (some people will stick to school holiday times). And, finally, suppose that you go on such trips five times per year. That’s probably more than most people go abroad for holidays, but possibly not for conferences. Again, it’s just a ballpark figure. Using those numbers means that you should expect to run into someone you know about once every five years. But you can see the ranges here by changing the numbers: If, for example, you go abroad once a year instead of five times, then the expectation is once every 25 years.
So a likely culprit seems to be similar social groups traveling to similar places. Do you think social media, and the way it can popularize certain destinations at any given time, is at play here?
Yes! This is certainly a factor. When at home, you will associate with people with similar interests and backgrounds, move in similar social classes, and so on. And, of course, it is therefore likely that those people will choose to go to similar overseas places as you. People with similar interests are likely to have similar social media experiences and hence be exposed to similar stimuli, making them aware of certain destinations. Of course, this is precisely what advertising also aims to do.
Is there a possibility that we run into people we know (from all corners of the world) more frequently than we think, but the phenomenon is just more salient while we’re abroad? Because it seems more fortuitous?
That’s an interesting question. I don’t know that we encounter people we know more frequently than we think, but certainly if it happens in a far flung place we attribute more surprise to it. That’s perhaps not unreasonable. If I run into someone I know at Waterloo Station (which I pass through quite often), I will take less note of it than if I encountered them in Birmingham, and even less than if I encountered them in Buenos Aires.
Perhaps it’d be helpful to explain, as an example, the factors at play when you take a train in the morning and see the same fellow passenger on the return journey.
Let’s start by considering how many people you noticed on the train down that you might recognise on the way back. Say it’s the people sitting near you on the train—say 10 people. Suppose that 8 of them will return later in the day (the 80% proportion will depend on many factors—is it a commuter run, is it the holiday season, etc.—but I’ve taken 80% as an illustration). We now need to know how many of them will pick your train to travel back on.
This will depend on how many other possible trains there are and on the time they want to return. If, for the sake of argument, I say there are 10 return trains, each with 500 seats, and each passenger randomly (unrealistic!) picks a train and seat to return on then there’s an 8/5000 = 0.0016 chance that they will be amongst the 8 people you would recognise on the way back. That’s a very small chance.
However, when one takes into account the fact that people will have made the journey to undertake some activity (work, shopping, a show, whatever) we see that their return is not random but is more likely to occur later. So this increases the chance. Finally, there are factors such as where you sit on a train. If this is your regular commute, not only may you take a regular train, but you may also have a favorite part of the train to sit in. And so may others, so that your chance of seeing them again is much higher.
This is why you should never pick lottery numbers like {1,2,3,4,5,6} or birthdays or particular patterns on the lottery slip, etc. If you have thought of those, then it’s likely that others will also. Indeed, typically thousands of people pick {1,2,3,4,5,6}. They are just as likely to win as those who pick another set of 6 numbers, but their winnings will be divided between many people.
What about a case in which you meet a stranger at an earlier point on your vacation, and then run into them again later in the trip? I suppose it’s more likely if they are also a tourist—as they’d be visiting similar sites—but what if they’re not? What if it’s in a different country?
Again, you have identified the main point. If you met someone during your vacation, they are likely to have similar interests to you, so perhaps it’s not so surprising to encounter them again later. It could be because they are tourists, or for work, etc. And “interests” here should be interpreted broadly—it could refer to a restaurant (one has been recommended), a show, etc. The main point is that whatever reasons drove you to go to wherever you are while traveling may well have driven them to do so also.
Are we more likely to run into more people while traveling simply because we are spending more time out in the world/on the go?
Yes! In doing this we are giving ourselves more opportunities to meet people. Perhaps I can add that there’s a parallel between your question and the issue of making oneself more lucky. If I change your question to “how can I make it more likely that I bump into someone I know when I’m abroad?,” one part of the answer would be “give myself more opportunities to bump into people I know.” And, with luck in general, one can give oneself more opportunities to be lucky. Someone who stays at home doing nothing, meeting no-one, reading nothing, and so on, cannot really be disappointed when nothing wonderful happens. But exposing oneself to opportunities (and grasping them) means one will get lucky more often. Of course, in a way it’s not luck, but basic mathematics!