From NYT's Upshot:
"According to a 2008 study, most children born in the summer tend to be among the youngest members of their class at school, which appears to explain why they are significantly less likely to hold leadership positionsduring high school and thus, another study indicates, less likely to landpremium jobs later in life. Similarly, according to research published in the journal Economics Letters in 2012, the number of American chief executives who were born in June and July is almost one-third lower than would be expected on the basis of chance alone. Even the first letter of a person’s last name can explain significant achievement gaps. Assistant professors in the 10 top-ranked American economics departments, for instance, were more likely to be promoted to tenure the earlier the first letter of their last names fell in the alphabet, a 2006 study found. Researchers attributed this to the custom in economics of listing co-authors’ names alphabetically on papers, noting that no similar effect existed for professors in psychology, whose names are not listed alphabetically."