During a 2007 study, scientists almost believed in astrology and horoscopes
Many of us have checked zodiac sign compatibility at least once. Some do it for fun, while for others it’s a very serious process that influences their choice of partner for building a happy family. Astrology has long since turned into a massive industry with apps, websites, and paid consultations. But what if we look at zodiac sign compatibility from a scientific perspective? Could it all actually work statistically?
The Connection Between Zodiac Signs from a Scientific Perspective
British sociologist David Voas took on the task of studying zodiac sign compatibility statistics in 2007. His research, described on Phys.org, remains one of the most large-scale studies in this field, and the results still provoke thought.
Voas used data from the 2001 census of England and Wales. At his disposal were records of more than 10 million married couples. These were not surveys or questionnaires, but real registered marriages with exact birth dates for both spouses.
The logic was simple: if certain zodiac signs truly suit each other better than others, this should show up in the statistics. There would be noticeably more couples with supposedly favorable sign combinations than random chance would predict.
Voas deliberately made the test as generous as possible for astrology. He didn’t test any one specific compatibility system but searched for any pattern at all. If Aries married Aries more often, Virgos married Capricorns, or women of one sign preferred men of another — all of this would count as an argument in favor of astrology.
Why Scientists Almost Believed in Astrology
At first glance, the data looked encouraging for horoscope enthusiasts. It turned out that people slightly more often married partners of the same zodiac sign — roughly 22,100 more couples than randomness would predict. If neighboring signs were also included, the excess grew to 26,900 couples.
Capricorns born in January stood out especially — among them, the number of “same-sign” couples was the highest.
The numbers sound impressive, but in percentage terms, it’s less than 0.25%. Still, it was a statistically significant result. It seemed like proof, didn’t it?
But then the problems began. The discovered pattern didn’t match any known astrological compatibility system. The most frequent pairings were not those that astrologers call “ideal.” No logic beyond matching signs could be found in the data. And astrology couldn’t explain why Capricorns supposedly gravitate toward other Capricorns either.
Why Horoscope Compatibility Doesn’t Exist
Voas decided to dig deeper. He ordered a detailed table with nearly 670,000 combinations of specific birth dates — not by zodiac signs, but by exact days and months.
And then something unexpected emerged. Spouses turned out to be born on the same day 41% more often than chance would predict. Instead of the expected 28,300 such couples, there were nearly 39,800.
The explanation had nothing to do with the stars. The census is filled out by one person for the entire household. Tired, distracted, can’t remember your spouse’s exact birth date — you accidentally write down your own. The same census discovered about 10,900 couples who accidentally registered as same-sex because the person filling out the form entered their own sex instead of their partner’s.
And the mystery of January Capricorns? The most popular “shared” birth date turned out to be January 1st. This date was systematically used as a placeholder when the exact birthday was unknown — for example, in nursing homes or with incomplete records.
When Voas excluded couples with birth dates falling on the first of the month and corrected the data for filling errors, all the magical horoscope-like patterns disappeared.
Why Horoscopes Seem Accurate
Voas’s study is interesting not only because it disproved the connection between zodiac signs and partner choice. It also demonstrated another important thing: even the fact that millions of people believe in astrology did not affect marriage statistics. You’d think that if a huge number of people read horoscopes and take them seriously, at least some should choose partners based on their sign. But in the real data, this effect was nowhere to be found.
So why are horoscopes so convincing for so many people? Psychologists have long described several mechanisms:
- The Barnum Effect — the tendency to accept vague descriptions as accurate. Phrases like “you sometimes doubt your decisions” apply to virtually anyone, yet each person reads them as a personal message;
- Confirmation bias — we remember the times a horoscope “hit the mark” and forget the misses. Over a year, enough such coincidences accumulate to create an illusion of accuracy;
- Self-fulfilling prophecies — if a person believes that Leos are energetic and confident, they begin to behave accordingly. A 1994 study showed that the connection between zodiac sign and personality traits was found only among people already familiar with astrological stereotypes.
In other words, astrology can influence how people describe themselves, but not what nature made them.
Should You Choose a Partner Based on Zodiac Sign
All available scientific data give a clear answer: no. No major study has found a connection between birth date and happy relationships. Stars and planets certainly influence many things — from tides to climate — but they don’t determine whom you’ll fall in love with or whether your marriage will be strong.
Relationship strength is influenced by entirely different things:
- The ability to listen and talk about difficult topics;
- Shared values and life goals;
- Willingness to compromise;
- Emotional support during tough times;
- Joint resolution of household and financial matters.
None of this depends on whether you were born in March or August.
Of course, one could argue that studies only tested “sun” signs, while real astrology accounts for the Moon’s position, the rising sign, houses, and aspects. But this creates a vicious circle. Popular astrology spent decades making simple and specific claims about zodiac sign compatibility. When those claims are tested and not confirmed, proponents retreat to more complex versions that are increasingly difficult to test.
None of this means that astrology is useless as a cultural phenomenon. For many people, it’s a way to talk about themselves, reflect on their qualities, or simply have fun. But making decisions about a partner based on their birth date is about as well-founded as choosing a life companion by their favorite color. Pleasant, but it has nothing to do with real compatibility.
