Originally Posted by HowlerKarma
It's also the reason why adoption studies in general are less useful than they used to be-- screening is SO thorough now that marginal/low SES homes are rare for adopted children.

Yes, but it goes even deeper than this. Agencies are screening the applicants, but applicants are also screening the agencies, so to speak. Applicants learn all about the process and what to expect, and can opt out at any time.

And we're talking about a self-selecting group even before the screenings begin.