Twins are fairly memorable. Unusual enough to remember, but common enough to know (just about everyone can claim "a friend of mine's a twin"). There are quite a few in the public conscience; an office straw produced the Krays, Olsens, Winklevosses and Barclays.
In a generation or so, my bet is that the list of notable (non-identical) twins will be longer. Firstly, there will be more of them. Secondly, that growing percentage of twins is growing up in tiger households.
There are four primary reasons for multiple births. "It runs in the family" (inherited on the mother's side) and a higher propensity within some ethnic groups; Nigeria has the highest multiple births rates in the world, for example, with Japan among the lowest. However, neither of these are increasing the overall number of multiple births.
Now to the two reasons the number of multiple births is increasing. The number of non-identical multiple births in the UK has been rising steadily for four decades. The Office for National Statistics (ONS) shows that in 1976, there were 9.6 multiple maternities per 1,000 maternities, rising to 16.1 in 2011 - that's a 68 per cent rise.
The trend is similar across most developed countries. In the US, the twin birth rate has risen to 33.3 per 1,000 (2009 figure) which is twice as common as in the UK.
The primary driver for the rise in multiple births across developed countries is IVF treatment, which commonly sees more than one egg implanted - increasing the chances of multiple births.
IVF treatment is available on the NHS in most parts of the UK, but it's restricted to a low number of cycles (exact allowances vary by region). That means that many IVF births are funded privately to at least some extent, which suggests financially comfortable parents. So a fair proportion of IVF-led multiple births are to (probably urban-based) professionals who aren't shy of a few quid.
In terms of parental effort, Susan Golombok, director of the Centre for Family Research at Cambridge University, highlights IVF-led parents as having had to have overcome so many obstacles to conceive that they make excellent parents (the same argument goes for same-sex, adoption, older and other 'modern families'). That's no slur on 'traditional' excellent parents of course, but her inference is that those who have overcome obstacles to having children in the first place are a rather undiluted collection of fully committed parents.
A secondary driver is that the likelihood of naturally conceived multiple births increases as the age of the mother rises (late 30s and into 40s). It is due to 'older' women being more likely to produce more than one egg during her fertility cycle.
Women aged over 40 have the highest rate of multiple births, and the number of women aged over 40 having children in the UK is at a record high (29,994 in 2012, up from just 6,519 in 2002).
According to ONS, the average age of mothers has risen to 29.8 years in 2012, compared to 27 in 1982. That is down to a range of factors including increased participation in higher education, a more female labour force, the increasing importance of a career, the rising opportunity costs of childbearing and the price of housing.
The trend is particularly acute in London. According to TGI (one of the baseline tools used by marketing people to track and define consumer trends and behaviour) the national average age for having a first baby is 31. In London, it is 33.
The propensity for naturally conceived multiple birth children, then, is to grow up in London (or cities in other developed countries) with slightly older career-focused parents. Like IVF-led multiple conception, typically aspirational tiger parents.
It makes for an interesting next generation of multiples born to economically and socially mobile parents. We're not talking from 'rich' families, as they wouldn't need to delay having a family in favour of career-building and maximising the earning potential. We're talking about the sharp-elbowed middle class, with money to pay for extra tuition, tennis clubs and all the rest of it.
It's pure conjecture on my part, as the data doesn't seem to exist, but my guess is that there is an increase in twin admissions to independent schools too.
Overall, the proportion of multiple births is still very low (about three per cent of the UK population), but big enough to attract marketing folk. The Twin and Multiple Birth Association (TAMBA), a charity that helps multiple birth families (bringing up multiple birth children is a huge challenge, absolutely exhausting and bloody expensive) has done a great job in attracting various retailers and service companies to offer big discounts to its members.
For forward-minded business, I'd suggest, it could become a good source for future recruitment initiatives too.