"What do Angela Merkel, Hillary Rodham Clinton, Christine Lagarde, Oprah Winfrey, Sheryl Sandberg, JK Rowling and Beyonce 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 Lisette Schuitemaker and Wies Enthoven set out to discover the big five qualities that characterize all eldest daughters to some degree. Eldest daughters are responsible, dutiful, thoughtful, expeditious and caring. Firstborns are more intelligent than their siblings, more proficient verbally and more motivated to perform. Yet at the same time they seriously doubt that they are good enough. Being an eldest daughter can have certain advantages, but the overbearing sense of responsibility often gets in the way. Parents may worry about their `difficult' eldest girl who wants to be perfect in everything she does whilst her siblings may not always understand her. "The Eldest Daughter Effect" shows how firstborn girls become who they are and offers insights that can give them more freedom to move. And parents will gain a better understanding of their firstborn children and can support them more fully on their way.