A friend tells me her mother is "fully Chinese", while her father is slightly Spanish, a little Iraqi and "a lot" Jewish. "I tick 'mixed other'," she adds, laughing. Throw "white British" into the mix and you have her daughter, whom she and her husband lovingly describe as "the mongrel".

As ethnicity winds its way down the generations, it creates a complicated yet wonderfully interesting web. Data from the Office for National Statistics suggests we can expect many more of these melting-pot families. Almost one in 10 Britons now lives with a spouse or partner from a different ethnic group.

When you dig deep into this fresh haul of figures, you happen across lovely details that pose fascinating questions about the psychology and sociology of love. Why is it that Chinese women are twice as likely as their male counterparts to be in inter-ethnic relationships (39% to 20%)? Or why is it Arab men – more than women – who will look a little further for love (43% to 26%)?

Overall, there are vast differences between ethnic groups when it comes to the ease with which they will cross cultural boundaries in search of romance. The most conservative are the "white British", "Bangladeshi" and "Pakistani" (4%, 7% and 9% respectively). Yet more than one in five "Africans" are falling for partners from different backgrounds, rising to more than four in 10 for "Caribbeans" and six in 10 for "other Black".

As for my friend – frankly, she would probably struggle to find anyone other than her sister with the exact same cultural mix. Still, it's interesting that the single most outward looking group is that of "mixed-race" people themselves, with 84% crossing an ethnic divide to form a long-term relationship. So other than giving us all a warm glow inside, why does any of this matter?

Because, as I'll argue, there is a significant economic benefit to be had when integration goes further than "when in Rome" and instead becomes a mass of social and romantic interactions. The first is to stress the scale of the societal change we are witnessing. On a personal level, I remember being acutely aware of the very few mixed-race couples I came across as a child. I was privately fascinated by the marriage of one Indian doctor to a tall, Dutch wife.

Things could not be more different now. I met the Chinese/Spanish/Iraqi/Jewish friend through NCT, a charity that brings together couples expecting babies at similar times in the same areas. Of the eight couples in our group (admittedly in a diverse London borough), four were in "mixed relationships". In 2012, it was a fact it took me a while even to notice. There was a Goan man and white British woman, a mixed-race Trinidadian with his blonde, Norwegian wife.

And then there was me. I'm one of 12% of Indians "marrying out". I've written on these pages before about the craziness that faced my white British husband, Toby, when he chose an Indian bride – from the wedding uniform of a turban, embroidered coat and "Aladdin" shoes to being swept up by a troupe of dancing relatives. Then there was India, with its endless "aunties" (any Indian woman older than us) thrusting gifts at him while smearing red marks on his forehead.

Since then, we've had a son who is half Indian, fairly English and a tad Welsh. His middle name is Trilok, his surname Jones. He is one of 6% of children under five of a mixed background. If he is "half and half", what will his children be, or their children? I suggest there comes a point when it stops being sensible to define people by increasingly blurred ethnicities that have no place on a page of tick-boxes.

Yet despite these big changes in parts of society, overall Britain remains ethnically pretty divided. Take the recent findings of the Social Integration Commission, a group chaired by RSA chief executive Matthew Taylor, who once led Tony Blair's New Labour policy unit. Its aim is to drill down into what an increasingly diverse Britain means for society, first by analysing the extent to which people of different ethnicities – but also of different age and social groups – interact.It found that the average Briton had 46% fewer social interaction with people from different ethnicities than they would if ethnicity were irrelevant

And yet it is class – not race – that drives the single biggest divide in our society. The fewest interactions take place between the top managers and professionals in socioeconomic group A and the casual labourers and unemployed classified in group E. And there was also an interesting, counterintuitive finding about the capital, which we all assume is the biggest melting pot of all. Once researchers took into account the diversity that exists in London, the number of social interactions across ethnic, age and social lines fell well short of what you would expect. In fact, they concluded it is one of the least integrated parts of Britain.

Now the group is embarking on the second part of its study – to measure the economic impact of such segregation. What could that be? Well, take, for example, the fact that 40% of jobs are found through people's networks. Or that the life chances of children are inextricably linked to their parents' backgrounds.

Now think of the price to society of the fact that the poorest, least economically active are terribly cut off from those at the top of the income scale. Or consider the impact of the fact that some ethnic groups are hugely under-represented in leading universities and the highest-paid professions. The work will undoubtedly uncover and quantify dozens of similar effects, proving that with whom you are friends and with whom you fall in love can have profound implications.

Yet despite the clear evidence that better integration makes for better society, our attitudes in this area appear to be hardening. According to the latest British Social Attitudes survey, three-quarters of Brits say they only consider those born here to be truly British and more than half insisting on the right ancestry. As well as cutting out the likes of the exceedingly British trio Boris Johnson, Joanna Lumley and Cliff Richard, that discounts me, my parents, my son, my NCT friends and millions more. It is an unthinking prejudice that could be deeply damaging to society if it leads to more reticence about integrating socially.

There's one particularly encouraging nugget that has emerged from the commission's work so far. While Britons don't always integrate well across ethnic groups, there is one stand-out group that does – and that is those who are mixed-race. They, more than any others, are willing to socialise across all ethnicities. And, as we know, sometimes these social interactions go a little further. A good excuse to welcome the news that such cross-cultural love is starting to spread.

Anushka Asthana is Sky News political correspondent