TO SAINT VALENTINE'S DAY

Mike Develin. Love and Religion

Mike Develin. The Age of Love

Mike Develin. Looking for Love

Bogdan State. Flings or Lifetimes? The Duration of Facebook Relationships

Carlos Greg Diuk. The Formation of Love

Adrien Friggeri. When Love Goes Awry

Invitation to Discuss the Read

Mike Develin. LOVE AND RELIGION

To kick off our Valentine's Day series, we take a look at the role that religion plays in the world of love. Religion is a major part of culture throughout the world; many countries are monolithic, but in other countries there is a significant mix of different religions coexisting. Today we look at this from the standpoint of romantic relationships. Let's take a look at a country-by-country plot of the percentage of actual same-religion relationships against the percentage of expected same-religion relationships:

The first thing that emerges from the data is that all countries have low rates of interfaith relationships. Spain has the highest rate of any country in the sample, and even there only 28% of relationships are between two people of different religions.

Among the countries in this chart, the United Kingdom has the lowest rate of expected same-religion relationships, and the second-lowest rate of actual same-religion relationships. In this sample, the UK is plurality Protestant, with Catholics, Atheists, and Muslims the most significant minority groups. This mix would be expected to produce only 21% same-religion relationships, but the actual rate is 73%. Even a melting pot of religions such as the UK still sees a large homophily effect in relationships.

However, the effect in the UK pales in comparison to other diverse countries like Taiwan, Singapore, and India. In Singapore, there is a large mix of religions -- the country is 50% Muslim, but 24% Protestant, 12% Catholic, 9% Buddhist, and 5% other. The religions, however, mainly keep to themselves -- over 90% of relationships are between people of the same religion. The situation in Taiwan is similar, with a 50% Protestant plurality, and minorities of 24% Muslim, 11% Catholic, and 11% Buddhist -- again despite this diverse mix, over 90% of relationships are between two people of the same religion.

Finally, Romania and Portugal stand out as countries with relatively high rates of interfaith marriage despite lower diversity. In Romania, Christian Orthodox is the main religion, with Protestant and Catholic minorities; in Portugal, Catholicism dominates, with Protestant and Atheist minorities. In both, we see significant rates of intermarriage, reflecting a more integrated society than in some other countries.

What affects whether or not marriages cross religious lines? One interesting finding is that people are generally more willing to date people of a different religion than they are to marry them, especially in their twenties. Restricting to the United States to remove country effects and to opposite-sex relationships thanks to the variation in gay marriage statutes, we obtain the following:

We see that, for instance, at age 25, 85% of marriages are between two people of the same religion, but 72% of unmarried relationships are. We also see that marriages between younger people are more likely to be interfaith than marriages between older people.

Overall, in the United States, 86% of relationships are between two people of the same religion. However, this varies significantly depending on which religion; these are the top religions listed by the US population on Facebook:

We see much stronger tendencies towards endogamy in some religions than others. Mormons and Sikhs, despite being small fractions of the overall population, tend to keep not only marriages but also other relationships within their religion; conversely, Jews, despite having fifteen times as many people in the US as Sikhs, are much more likely to intermarry. Finally, as you might expect, Jedi have the highest likelihood of intermarriage -- it is hard to find someone with compatible midichlorians. Although considering that Jedi comprise only 0.15% of the population, it is still a rather impressive use of the Force that 13.2% of Jedi manage to find another Jedi to marry.

Check back in tomorrow, when we'll continue with a post on age difference between partners in a relationship.

The data for this research consists of romantic relationships between two people from the same country, age 21+, both with self-identified religions. Religions were classified into one of seventeen main categories, and people with religions not falling into one of these were discarded from the sample. Since we only use self-identified religions, there is likely some effect due to selection bias: those indicating their religion on Facebook are likely to be more religious and presumably less likely to intermarry. The term relationship encompasses pairs of people who are either In a Relationship, Engaged, or Married on Facebook.