There is no need to guess about the statistic or give reasons why it may be flawed when the studies are out for you to read for yourself and find out how they came to that conclusion. You can also see if they have already addressed the issues that you have brought up.
Cohabitation is good and all when both parties agree to it but most women and men still want to get married. So you are with some one who wants to get married and you don't for the most part no matter how "in love" they are with you they will leave to find some one that can better answer their needs.
You are not being objective yourself when looking at the problem.
While not the same the problem is something like this.
And outside party forces a woman to carry a child to term that she does not want or cannot care for. Once the child is born family law state that because it is in the best interest for the child the woman must pay 20% of her income for the next 21 years to take care of the child. Is that right? This is what basically happens to men in a situation when an unwanted pregnancy happens. Due to nature men have no control, once a woman gets pregnant, of his reproductive rights and after the child is born family law states the man has do what is in the best interest for the child. Now if the man has stated before hand where he stands in regards to his reproductive rights and the woman agreed to them but later reneges and forces the man to pay child support for the child how is that fair? If a man states his wishes in regards to his own reproductive rights before a child is conceived is it right that a woman can just wave it off as if it does not matter and proceed to do has she wishes. If you say yes, no matter how good the reason, you are saying yes to violating a mans reproductive rights.
I will say this again I don't agree with men being given the choice to walk away after a child have been conceived but I do believe that men should be able to have their reproductive wishes up held legally if they have given the woman informed consent and she has agreed to it before a child is conceived. It gives men some measure of control of their reproductive rights after a child is born if they have may their wishes clear to a woman.
If you want to progress past that, with me at least, explain to me how the best interest of a child trumps having someone's reproductive rights violated?