Do you mean to be so rude, iwanttomove?
I linked to the source for CP stats in an earlier post, and that page links to the respective page for marriage stats. Your quoted numbers above are incorrect because they are for total number of marriages in England and Wales, not number of same-sex marriages. The ratio I referenced above was explicitly "For every 5-6 marriages between same-sex couples, there's 1 new CP".
When you look at the correct numbers, my quoted ratio is supported:
2014: Same-sex marriages 4850; Civil partnerships 1683
2015: Same-sex marriages 6493; Civil partnerships 861
When those two years are pooled to smooth out variability - a common approach in calculating ratios of events - you get the following:
2014-15: Same-sex marriages 11343; Civil partnerships 2544
= ratio 5.5:1
Since the ONS has a lag reporting the marriage numbers in England and Wales for 2016 and 2017, we can't make the same direct comparison for those years. However, we do know that the number of CPs per year has stayed stable (indeed, increased slightly) for 2016-17, so it's not a case of CP numbers dwindling away. It's possible that the number of same-sex marriages has continued to increase 2016-17, but we don't have any evidence of that at the current time.
Therefore, on the basis of the most recent figures available, I stand by the assertion that, in England and Wales, for every 5-6 marriages between same-sex couples, there's 1 new civil partnership.
I hope your job doesn't involve teaching maths or accounts
Part of my job (as a STEM academic) involves lecturing university students in statistics and research methods. Attention to detail, such as selecting the correct comparison group, is a critical component of valid statistical design and analysis. I don't insult students who make mistakes, however.