The first pecking order

Sure, Mom and Dad may say they love all the kids equally but the foundations for inequality in later life begin at home, says sociologist Dalton Conley.

Because, says Conley, families develop pecking orders that are shaped by larger social forces and their own changing circumstances. Economic ups and downs, wars, tax policies, access to health care -- even the timing of a divorce -- create ripples that may carry a family's children in different directions.

That's especially true in lower-income families, he says in his new book, "The Pecking Order: Which Siblings Succeed and Why" (Pantheon, 309 pages, $24), because parents often invest the bulk of their limited resources in one promising child.

Which leads to Conley's most startling claim -- that 75 percent of the income inequality in the United States is within families, not between them. Learning how siblings diverge, he says, could shed light on why some of us are poor, others rich.

Read more of P-I reporter Cecelia Goodnow's exploration of Conley's book. Other sociologists tell Goodnow that they're skeptical of his thesis -- but admit they haven't read his book.