Do 'compatible' zodiac signs marry more durably? Swedish population data answer

Short answer: population data do not confirm that 'compatible signs' make marriage last

Jonas Helgertz and Kirk Scott published in 2020 in the journal Genus an analysis tracking the entire Swedish population from 1968 to 2001, comparing spouses' Sun signs with their likelihood of marrying and divorcing. The results showed no consistent evidence that couples astrologically considered compatible tend to marry more often, or divorce less, than other couples.

This is one of the few studies using national population register data instead of self-reported questionnaires, so it answers the question on a much larger scale than small surveys. But its scope is clear: Sweden, 1968-2001, and only Western astrological Sun signs. This result does not automatically apply to Vietnamese people, and says nothing about zodiac age compatibility.

Why is population register data stronger than surveys?

Population register data are stronger than surveys on three points: no one self-selects into the sample, no one misremembers, and no one is left out.

• No self-selection: surveys often rely on volunteers. Volunteers may differ from non-respondents in many characteristics, including interest in astrology. Population register data cover the entire registered population, regardless of willingness to participate.
• No misremembering: when asked about birth dates, wedding dates, or marital status, respondents may misremember, merge memories, or answer as they wish were true. Registration records capture events at the time they occur.
• No one left out: people who divorce and remarry, or move between localities, all leave traces in the registration system. Surveys easily drop these groups.

Gerhard Mayer, in a literature review published in the Journal of Scientific Exploration in 2020, summarized a series of methodological problems in astrological research: available astrological knowledge biases self-reports, personality questionnaires measure the gap between ideal self-image and actual behavior, and an event like 'marriage' is treated as a clear fact while marriage for love, convenience, or coercion are entirely different things. Population register data avoid most of these problems because they do not ask how anyone feels, they record what people did.

What did the Swedish study do and find?

Helgertz and Scott's study used Swedish population register records to track married couples over decades, comparing couples whose Sun signs are traditionally considered compatible with the rest. The authors tested both directions: whether two people with compatible signs were more likely to marry, and whether such marriages were more likely to break down.

The team concluded there was no consistent evidence in either direction. In other words, whether two people belong to a supposedly compatible sign pair did not predict whether they would marry, nor whether their marriage would be more durable or more fragile than the population baseline.

It must be clear this is a result for the Swedish population 1968-2001. Swedes marry, divorce, and organize family life according to their own cultural and legal norms, different from Vietnam. There is no basis to apply this result to Vietnamese people without research on Vietnamese people.

Why is this question hard to answer with small surveys?

Three obstacles make small surveys poor at answering the question of sign compatibility and marriage: sampling, recall, and expectation.

Mayer 2020 noted that pre-existing astrological knowledge, even just from newspapers or sugar packets, is enough to bias self-reported personality. If respondents already know how their sign is described, they tend to answer according to that description. This effect occurs not only with astrology enthusiasts but also with those who have only heard it in passing.

Another obstacle is that marriage is not a single-meaning fact. Mayer 2020 cited the view of reform astrologers: marriage for love, for convenience, or under coercion are different things, and if research lumps them into one variable 'married', the potential signal is diluted. This applies to both astrological research and marriage research in general.

'Special' wedding dates and divorce risk: what do Dutch data say?

Jan Kabátek and David C. Ribar published in 2018 in the Journal of Population Economics an analysis of couples who married on dates considered special, such as repeated-digit dates or Valentine's Day. Result: this group had a higher-than-average divorce risk, but most of the difference came from pre-existing characteristics of the couples rather than from the wedding date itself.

This is an important methodological point. When a group has a higher divorce rate, the next question is always: is the difference in the wedding date itself, or in who chose that date? If couples choosing special dates already differ in age, income, education, religion, or degree of belief in symbols, the higher divorce rate may reflect those differences, not the effect of the date.

Kind of knowledge: Folk beliefFolk belief. What people believe, avoid or pass on by word of mouth, recorded as a belief, not as a checked fact. The five labelsIn folk beliefs in many places, including Vietnam, choosing an auspicious day and month for the wedding is considered an important step for a smooth marriage. Phan Kế Bính, in the book Việt Nam phong tục published in 1915, recorded that before the wedding, the groom's family had to choose an auspicious day and month before agreeing on the wedding date with the bride's family. This is a record of custom, not evidence that the wedding date determines marriage durability.

The question Vietnamese people ask more often: are Rat and Horse years compatible?

Kind of knowledge: UnprovenNot enough evidence. Someone has claimed it, but no source or study is strong enough to confirm it. The five labelsNo study in the literature examines zodiac age compatibility, cung phi, or Tam Hợp with marriage outcomes in Vietnam or East Asia. This is the largest gap between search demand and available evidence.

Vietnamese people ask about Rat and Horse years, about Tam Hợp, about cung phi, more than about Western zodiac signs. But the large-scale population studies available, such as Helgertz and Scott's Swedish study, only test Western astrological Sun signs. There is no equivalent study for the zodiac animal system.

Kind of knowledge: Folk beliefFolk belief. What people believe, avoid or pass on by word of mouth, recorded as a belief, not as a checked fact. The five labelsIn folk belief, people believe some age pairs clash, and marriage between those two ages will face obstacles. This belief is passed down through families, through age-reading practitioners, through reference books. It has real social weight: many couples face family opposition because of age clash. But social weight does not equal scientific evidence. Currently, both directions are missing: no study confirms, and no study refutes, at population scale.

Kind of knowledge: SchoolSchool's interpretation. How one school or one book reads it; other schools may read it differently. The five labelsIn Eastern systems, relations between ages are determined by each system's rules: Tam Hợp, Tứ Hành Xung, Lục Hợp, cung phi. These rules may differ between books, and a couple may be considered clashing by one system while another considers them normal. This is a feature of rule systems, not evidence about marriage outcomes.

Why are researchers skeptical of astrology in general?

Shawn Carlson published in 1985 in Nature a double-blind test: astrologers received natal charts and personality descriptions and had to match them correctly. The results showed the match rate was no higher than chance. This is one of the most cited experiments in the field.

I. W. Kelly published in 1997 in Psychological Reports a critical review of modern astrology. Two main points: astrology provides no mechanism to explain why celestial positions relate to human personality or fate; and when astrological systems conflict, there is no way to adjudicate which is correct.

Mayer 2020 recalled an observation by Geoffrey Dean, a former astrologer turned skeptic: successful double-blind tests, if any, do not prove astrology correct, but only prove that astrologers are working. Dean's interpretation is one way to read the results, not the only conclusion. But it raises the right question: when a practitioner reads a chart for a client, good results may come from conversational skill, psychological knowledge, ability to read the client's reactions, not necessarily from the chart.

Real effects born from belief: what are they called?

There are real effects, but they are born from belief, not from rule systems. Belief changes behavior, behavior changes outcomes.

An easy example: if a couple believes their signs are compatible, they may invest more in reconciliation during conflict, or overlook small differences as trivial. Conversely, if a couple believes their ages clash, they may attribute every conflict to the chart, reduce repair efforts, and divorce faster. In both cases, the outcome comes from belief-driven behavior, not from celestial positions or zodiac animals.

L. Dow Balliett, in the book Attain Success Through Vibration published in 1917, presented a method for calculating 'vibration' for names and dates, and argued that if spouses both live according to the 'vibration' of the marriage name, they could become harmonious again. This is an example showing that occult systems themselves are aware that outcomes depend on whether people follow them. It also shows that numerology based on names and birth dates formed in the late 19th and early 20th centuries, borrowing Pythagoras's number philosophy rather than directly inheriting from him.

This distinction matters because it avoids two extremes. One extreme is calling every good outcome of a believer evidence that the system predicted correctly. The other is denying that belief can create real differences in behavior and outcomes. Both are wrong.

Nhật Nguyệt's suggestion: making room for the utility of age reading

Nhật Nguyệt's suggestion: if you are troubled because your family opposes the match due to age clash, the useful thing is not to try to prove the chart right or wrong, but to separate two questions.

First question: what specifically is the family worried about? Usually it is not the zodiac animal itself, but fear that the children will suffer later, fear of conflict, fear of losing face with relatives. These are concerns that can be discussed.

Second question: what does marriage research actually know is related to durability? Widely studied factors include age at marriage, education, income, degree of shared responsibility, conflict resolution style, and level of commitment. These are things that can be improved through behavior, unlike zodiac animals or zodiac signs which cannot be changed.

The utility of age reading and sign reading has its place as a cultural activity, a way for two families to discuss, an occasion to look back at one's own wishes. It should not stand in the position of deciding in place of the factors that marriage research has shown to be related to durability.

Conclusion

For zodiac signs, Swedish population data 1968-2001 show no evidence that 'compatible signs' make marriage more durable or more fragile. This result is for Sweden, and does not automatically apply to Vietnamese people.

For zodiac animals and age compatibility, there is no data. This article does not conclude on their behalf. It is a folk belief not yet tested at population scale, and that gap remains.