They were using Tu Vi, an ancient belief system in Vietnam with Taoist roots stretching back to at least 16th century China. Tu Vi offers individuals and couples predictions about future events—such as marriages, births, deaths, business prospects, and travels. These are based on a person’s time of birth and lunar birth year in the 12-year zodiac cycle.
Tu Vi’s popularity in Vietnam has ebbed and flowed in the 20th century, and it regained widespread popularity in the past 30 years. But little is known about whether these sorts of religious belief systems, which are independent of any institutions or doctrine, affect people’s behavior.
In particular, Nguyen wondered how much these beliefs really matter to couples when it comes to making marriage decisions. She also wondered: What are the implications for their marriages if they do have what Tu Vi considers an auspicious match?
To explore these questions, Nguyen collaborated with Edoardo Ciscato, at KU Leuven, and Quoc-Anh Do, at Monash University. They found that Tu Vi is a pervasive and important part of Vietnamese life.
More so, they also found that couples in what are deemed auspicious marriages benefit in measurable ways: they earn more and have a higher standard of living, for example, and their children are less likely to drop out of school.
Which is not to say that the stars were right in their predictions. Nguyen says that there’s a self-fulfilling prophecy at work: when a couple’s social circle believes a marriage is auspicious, they are more likely to step in and offer help, buoying the couple through hard times.
“Auspicious couples indeed end up doing better, and this belief is passed down through generations,” Nguyen says.
Assessing how much Tu Vi matters
The researchers collaborated with a think tank to conduct a survey of ethnic Vietnamese people in 2020. The results highlighted how prevalent Tu Vi is: eighty-two percent knew about the system and how to get information on detailed predictions; 45 percent believed that their family and relatives care about Tu Vi; and 31 percent considered Tu Vi to some extent in their own marriage.
To understand how much these beliefs in marital fortune influence marriage formation, the researchers turned to census data, as well as data from the Vietnamese Population Survey, focusing specifically on four regions of the country, two urban and two rural. From the 2009 census, they analyzed a sample of 916,314 married couples. Women in this sample ranged in age from 19 to 33 years old, while men ranged in age from 21 to 35. Researchers also analyzed similar, but smaller, datasets on couples in the 1989 and 1999 censuses, as well as Population Survey data from 2006-2018. In all, the different samples include 1.36 million couples.