yetanotheranyfucker I haven't delved into the info sources sorry, so I can't say either way. There are 43 sources, so Im not about to try! 
That doesn't mean that 62% of NRPs don't pay though because there isn't a 1 to 1 relationship between number of RPs and NRPs. Also it doesn't tell is how many are choosing not to get maintenance or the reasons
Well it does mean 62% don't pay, if 38% do pay, then 62% don't.
Whatever the reasons, that is still 62% who don't pay.
What do you mean by there isn't a 1-1 relationship between a number of RPs and NRPs? Do you mean no contact between the adults whatsoever?
If that is what you mean, I don't see how it makes a difference? it's still part of the non payment category.
If you have 100 single mothers, that could be 50 fathers. If only 38 mothers are receiving maintence, it could be that 33 out of the 50 fathers are paying i.e. the majority of them. It stands to reason that fathers with 3, 4, 5, 6 children who they have fathered without a backward glance are going to be less likely to pay and will therefore account for more single mothers not receiving maintenance
It could be but I doubt it.
I know there are men that have children with more than one mother, I know that some of them 'pick' which ones they support and which they don't, so a paying NRP could also be in the non paying category. Despite being a payer on one hand, he is still a non payer.