First off you will NEVER know accurately how many people have gone through childhood neglect. There is no way of getting that number.
Second....childhood neglect is like a spectrum thing. My childhood neglect was different from those parents with high drive for their kids. My parents had no drive & minimal education so they could function...also because of their own mental states were not well capable of functioning in society so I never was able to learn from them.. I had to figure it out on my own & all I really grasped was that there was so much more to life than I ever experienced growing up. I never figured out what my parents issues were or my husbands (another story that ties in) until I was in my late 50's & had left my bad marriage.....& during those years I fought to get my BS degree & have a computer engineering career.
People have gone through all different levels (kinds) of CEN....& each come out differently even though they have gone through it....the effects are different. The symptoms aren't neately packaged like the DSM symptoms & the neglect that happened isn't either