When you’re online dating, why do you swipe left on one person and swipe right on another?

Are you carefully weighing every factor that makes someone a good romantic match?

Those 30 million people have generated billions of pieces of data.

And because most dating sites ask users to give consent for their data to be used for research purposes, this online courting has played out like an enormous social science experiment, recording people's moment-by-moment interactions and judgments.

A team led by Elizabeth Bruch, a sociologist at the University of Michigan, Ann Arbor, tapped into this torrent of dating data.

Because of a nondisclosure agreement, the researchers can't reveal the exact source of their subjects, describing it only as an "established, marriage-oriented, subscription-based dating site" from which they randomly selected 1855 people, all based in New York City.

Besides photographs, each user's profile could include any number of personal details including age, height, weight, education, marital status, number of children, and smoking and drinking habits.

The data set includes some 1.1 million interactions between users.But beyond someone's looks, how much do any of these factors matter for mate selection?One complication is that online daters are not making just one decision, but several in a series: First, people are swiping their way through profiles and deciding which to dismiss immediately or browse more closely.Then comes the choice to send a person a message, or to reply to one.And of course, the final, crucial decision, which isn't captured by these data: whether to meet the person in the real world.Bruch's team devised a statistical model that maps the "decision rules" people follow during the first two steps.