The Eldest Daughter Effect: How Firstborn Women - like Oprah Winfrey, Sheryl Sandberg, JK Rowling and Beyonc - Harness their Strengths

"What do Angela Merkel, Hillary Rodham Clinton, Christine Lagarde, Oprah Winfrey, Sheryl Sandberg, JK Rowling and Beyoncé have in common?" was the headline in the English newspaper The Observer in 2014. "Other than riding high in Forbes list of the world's most powerful women," journalist Tracy McVeigh wrote in answer to her own question, "they are also all firstborn children in their families. Firstborn children really do excel."

So what does it mean to be an eldest daughter?

Firstborns Li...