It is perhaps the most commonly repeated piece of relationship advice. "There are plenty of fish in the sea" has been uttered by those helping friends through breakup and rejection and by those frustrated with dating to soothe themselves. But is it true? Given the complexities in compatibility and attractiveness, I would say no. The number of fish is likely much smaller than people actually believe.
Since dating is just a "numbers game" allow me to actually do some numerical calculations for you.
Calculating How Many 'Fish' There Actually Are
So let’s begin with the most obvious figure. There are roughly 7.4 billion people on Earth. According to US demographics, around 7% are within reasonable range of my age (22), leaving 518 million.
Next, I’m heterosexual, so we must naturally eliminate the males from this pool. For most populations, the natural male/female ratio is 1.05 males/females, so we can eliminate around 51%, leaving 253 million.
Obviously, the sexual orientation of this pool has to be taken into consideration, so around 1.7% can be removed since this is roughly the percentage that identify as lesbian. This leaves 249 million.
Now comes the issue of height. I’m around 5’9” (roughly average) and while I would date a girl taller than me, I can safely assume that most girls would be uncomfortable with this, so they will also be eliminated. According to US statistics, around 3.8% of females are taller than me. Eliminating that demographic leaves 240 million.
Rough calculations (based on US statistics) from online forums suggest that about 25% of people are effectively single, which dramatically reduces the aforementioned number to 60 million. Note: This assumes that being in a relationship is not dependent on any of the other factors used in this calculation.
While this may be inaccurate, let’s assume for the sake of simplicity that I am of average attractiveness, meaning that I could potentially date anyone at or below average physical attractiveness. This limits the pool to 30 million. Note: People often want their partner to be of similar physical attractiveness to themselves. This value is hence very generous. Furthermore it is likely that for someone very attractive or very ugly, the odds would decrease significantly.
The language barrier wouldn’t be much of an issue for me since people I am compatible with are likely highly educated (and hence, probably speak English). For some, where this isn’t necessarily the case, the language barrier can be a significant problem. Around 38% of the world population can converse relatively well in English, so for English speakers their pool is now limited to around 11.5 million.
As for the somewhat contentious issue of intelligence, taking the simple approach and assuming my intelligence is roughly average and that I could be compatible with anyone 1 standard deviation away from me, leaves about 70% which reduces the pool to around 8 million. Note: According to intelligence tests and academic performance, I'm actually 2 - 4 standard deviations above the mean, so this figure is very conservative in my case. See the note below.
Important Note: Using the 1 standard deviation difference rule seems reasonable to me (though it is very unscientific and simplistic). However, using it clearly creates significant difficulties for those in the higher (or lower) brackets of intelligence. Those that are average have the most options using this methodology (around 70% pool availability). Someone 1 standard deviation above the mean would be limited to around 50%. Someone 2 standard deviations above the mean would be limited to around 15.7%. Three standard deviations, and likely only 2.2% will be compatible and so forth.
In my opinion, the aforementioned factors are the bare minimum in establishing compatibility. Once these criteria are met, there is a whole slew of other factors like culture, faith, interests, sexual compatibility, etc. An anecdotal figure which may or may not be accurate is 5%. That is, 5% of people who meet these basic requirements will be compatible enough with you so as to actually consider a relationship with them. This reduces the figure to a rather puny 400000.
Assuming that one were to live in a relatively large city of about 1 million, this means a pool of roughly 50 people (without correcting for urban demographics and the cultural/lingual homogeneity of the city). That’s it. Even without the unscientific 5% added for overall compatibility, the pool is still relatively small with only around 1000 people present in a city of 1 million.
In a city of 1 million, there may be as little as 50 people whom you are compatible with. This number may be much smaller for those with rarer personality traits, are very attractive and/or very intelligent.
For the rare individual that is above average in terms of both appearance and intelligence, the pool could shrink to as little as 10 people in a large city.
Pinpointing a Better Compatibility Figure
The 5% figure used earlier was at best a guess and will likely differ from person to person. It may be instructive to actually calculate a more specific value and I’ll use myself as an example, just as a sort of sanity check.
The first thing that is relatively important to me is that I don’t drink alcohol. It would probably be better for me and the other person involved if we shared this trait. According to US statistics around 30% of people don’t drink.
Next we can use the “16 personalities” test to determine about what percentage of the population would make a good match. Taking the recommendations of 16personalities.com for my personality type, about 21% of the population would make a good match romantically. As you can already see the probability is now at around 6.3%.
There are certainly more traits that could refine the figure, but I believe that the 5% estimate made earlier is actually pretty accurate for me and probably most people which is pretty cool.
The calculation is definitely not perfect and makes many assumptions about the nature of attractiveness and what people truly look for in a relationship. In particular the calculation is based primarily on “compatibility” which may mean different things to different people. Furthermore, what actually determines compatibility is subject to speculation. This analysis is mostly intuitive and at best a rough estimate but I feel as though its findings are corroborated by my real world experience and the frustration of people looking for relationships everywhere. Perhaps there really are less fish in the sea than your friends tell you there are.
If you see any problem with my calculations or would like to contribute your own input, please do. I'm not absolutely certain about any of these calculations and would really be interested in refining them as much as possible. Some of the calculations make assumptions about the statistical independence of the factors which would skew the result a little towards a lower value.