Excellent article in the latest TIME magazine by Dan Cray.
"Of all the things that shape who we are, few seem more arbitrary than the sequence in which we and our siblings pop out of the womb. Maybe it's your genes that make you a gifted athlete, your training that makes you an accomplished actress, an accident of brain chemistry that makes you a drunk instead of a President. But in family after family, case study after case study, the simple roll of the birth-date dice has an odd and arbitrary power all its own.
The importance of birth order has been known—or at least suspected—for years. But increasingly, there's hard evidence of its impact."
Link to Time article 'The Power of Birth Order'.