According to author Ralph Richard Banks, black women are half as likely as white women to be married, and they are more than three times as likely as white women never to marry.

Why? Banks, a Stanford Law professor, tries to answer this question in a new book titled “Is Marriage for White People? How the African American Marriage Decline Affects Everyone.”

Although it is not an advice book, one of Banks’ arguments is that black women’s loyalty to and patience with black men is noble yet counterproductive, and they should consider men outside the black community. This notion has sparked significant controversy and debate.

Sixty years ago, black marriages and families were “as stable as white families,” Banks said in an interview with “Nightline” for a story airing tonight. The decline has been complex, but a key factor is that “as black women have moved ahead, black men have fallen behind,” he said.

“Nightline” first examined this phenomenon and its relation to the larger issue in a 2009 story that provoked a huge response. This paved the way for a “Nightline Face-Off” debate held in 2010 in Atlanta.

Follow the links to learn more and join the discussion.