The Office of National Statistics recently answered this question: How many marriages of same sex couples have been formed in England and Wales so far?
ONS looks at the first provisional statistics between 29th March and 30th June 2014.
This is the first time that ONS has published provisional statistics on marriage of same sex couples for England and Wales. These statistics cover quarters 1 and 2, 2014. The Marriages (Same Sex Couples) Act 2013 made provision for the marriage of same sex couples in England and Wales, either in a civil ceremony (in a register office or approved premise such as a hotel) or on religious premises (provided that the religious organisation agrees). The first marriages of same sex couples took place on 29 March 2014. From 10 December 2014 civil partners are expected to be able to convert their civil partnership into a marriage.
How many marriages have been formed between same sex couples?
A total of 1,409 marriages were formed between same sex couples between 29 March and 30 June 2014. Of these, 56% of marriages were to female couples (796 marriages) while 44% were to male couples (613 marriages). Over the three day period from 29 March to 31 March 2014 there were 95 marriages of same sex couples. There were 351 marriages in April, 465 in May and 498 in June (Figure 1).
And there is a lot more detail on the sex, age, etc. of the couples.
Law & Religion UK provided some further analysis and comment: Same sex marriage statistics: 2014, Q1 & Q2 which includes:
However, it could be argued that although there is now the possibility of same sex marriage in England and Wales, latest ONS data indicate that up to the end of 2012, a total of 60,454 civil partnerships had been formed, and until 10 December 2014 none of these nor those formed subsequently will be able to be converted into a same sex marriage. We therefore await the statistics for Q4 with interest.
And the same site had earlier provided an update on Civil partnership conversion to same-sex marriage: religious content which, in addition to dealing with the subject contained in the article title, includes the following observation (emphasis added):
From the legal point of view, the conversion process is essentially an interim measure directed at couples who entered into civil partnerships between its introduction in 2005 and the availability of same-sex marriage in 2014. Nevertheless, within this period a significant number of civil partnerships have been formed: latest data from ONS indicate that since the Civil Partnership Act 2004 came into force in December 2005, there were 60,454 civil partnerships up to the end of 2012, i.e. 120,908 civil partners, an order of magnitude greater than the 11,000 to 22,000 civil partners estimated in the regulatory impact assessment. The ONS is currently examining the trends in civil partnerships, how marriages to same sex couples will change the statistics, and how this might best be reported, here and here.
With regard to the conversion process, government priorities appear to be: meeting the 10 December 2014 deadline; and reflecting the responses in its 2012 consultation. The delay caused by the withdrawal of the draft statutory instrument, and the potential complications associated with the introduction of a religious element are likely to limit the changes that may be introduced at this late stage. Furthermore, the potentially large number of couples wishing to convert their civil partnerships to same sex marriages may also preclude changing the proposed procedure unless present resources are augmented2.
2 There were ~183,000 civil marriage ceremonies in 2012, ONS data.
So, to consider a possible scenario, if around 50% of all extant Civil Partnerships were converted in the six month period from December, that would be an increase from around 500 a month to around 5,000 a month. And an additional 30,000 same-sex marriages on top of (say) 90,000 heterosexual marriages. Which is quite a large temporary fluctuation.