By Padraig BeltonTechnology of Business reporter
13 February 2018
How many couples will have met online this Valentine's Day? More than ever before is the safe answer, as online dating continues to sweep the world.
But is data crunching the best way to find a partner?
In the future, a computer program could dictate who you date, and for how long. This was the premise of a December 2017 episode of Black Mirror, the dystopian sci-fi TV series.
But technology already has radically changed romance, with online dating growing massively in popularity ever since Match.com blazed a trail in the mid-90s.
Now apps, such as Tinder, with their speedy account set-ups and "swipe to like" approach, have taken dating to another level.
Tinder launched in 2012 on the back of the explosion in smartphone use. Just two years later it was registering more than a billion "swipes" a day.
In America's last presidential election, the Democratic campaign logo encouraged voters to "swipe right for Hillary".
Jordan Brown, a 24-year-old blogger, says she "had a bit of a swipe" in October 2016, and met her current boyfriend, who lived an hour-and-a-half away. She would not have met him otherwise, she says, adding that the two bonded over a shared love of Disney.
When 30-year-old Sara Scarlett moved to Dubai in 2015, she joined Tinder to meet new people. She met her last boyfriend after a month. But converting swipes to dates can be difficult, she says.
"You spend ages chatting to these guys and then they don't even want to go for a coffee," she says.
Swapping swiping for supper dates also proved a problem for Jordan.
"There are hundreds of timewasters, losers, and just general muppets on there who have nothing better to do than mess you around," she observes.
Despite such frustrations, dating apps have grown relentlessly. Worldwide spend was £234m in 2016, but nearly double that - £448m - in 2017, says app research firm App Annie.
Pew Research found that 59% of adults now think online dating is a good way to meet people. Even in 2005, 20% of same-sex couples were meeting online. That rocketed to 70% by 2010, say sociologists Michael Rosenfeld and Reuben Thomas.
Online dating has been particularly useful for gay men, as homosexuality is still punishable by death in five countries and parts of two others, says Grindr's Jack Harrison-Quintana.
"The fundamental reason dating apps were created in the gay community was to protect users and create a safe environment, no matter where they are located," he says.
Dating apps made up three of the top 10 apps by consumer spend last year in the UK, says Paul Barnes, a director at App Annie. In France, home of romance, they accounted for six of the top 10.
"There's a lot of money here and it's a lot more competitive now," says Mr Barnes, "so app makers really have to understand their users very well, and find ways to keep them engaged."
Traditionally, dating services required members fill in exhaustive questionnaires. Now machine learning is also being marshalled in the quest for better matches.
A small amount of text - 300 to 400 words from Twitter posts - is enough for their software to decide how much two people will have in common, claims Daigo Smith, co-founder of LoveFlutter.
LoveFlutter has paired up with Toronto-based natural language processing firm Receptiviti to create new approaches to matching people that they will start using this year.
These draw on research by James Pennebaker, a social psychology professor at the University of Austin, Texas. Prof Pennebaker studied 86 couples and found partners using similar frequencies of function words - articles, conjunctions, and pronouns - were most likely still to be together after three months.
Another data-based approach is to use your smartphone's location to find potential dates.
Paris-based app happn analyses where you have been during the day, then shows you people who passed within 250 metres of you. These people will be easiest to meet in real life, says Claire Certain, happn's head of trends.
"It's really just about meeting and giving it a try. If it's going to be a good match or not is very mysterious, chemistry is very surprising."
But if proximity solves the problem of endless swiping but no suppers, it can also mean we stay within our social silos, warns sociologist Josue Ortega. Whereas online dating has increased the incidence of interracial dating, he says.
Rachel Katz, an American who studied Tinder for her master's degree at Cambridge University and is now studying Grindr for her doctorate, agrees.
"Once, most people married people who lived within four miles of them. Then we had the internet, and all these infinite possibilities for soulmates across the world; it didn't matter where they were."
But in 2018, physical location is of primary importance again, says Ms Katz, "so you're going to meet someone who's conveniently close - but this also replicates boundaries of class."
The next tech wave in online dating will feature augmented and virtual reality, the experts believe.
Imagine scanning people with your phone in a nightclub and seeing how many have made their dating profiles available, says happn's Claire Certain.
And LoveFlutter's Daigo Smith says: "Rather than going to a bar, you'll spend your evening going into virtual bars buying other avatars virtual drinks with your cryptocurrency."
But one enduring complaint against dating apps is that they're not very female friendly.
The percentage of women on dating apps "never goes above 35%", says Jean Meyer, founder and chief executive of Once Dating. Men, it seems, often don't behave like gentlemen.
On Mr Meyer's app, women leave feedback about the men they've dated. And maybe men will learn from this feedback, he says.
Austin-based Whitney Wolfe Herd, a former Tinder vice-president, launched an app called Bumble which relies on women to make the first contact with men. The firm - where 85% of staff are women - is now valued at over $1bn, according to Forbes magazine.
So online dating is here to stay - and will embrace new technologies as they emerge - but when it comes to love, there are no guarantees.