"From the Archives", first published in the Digest 27.10.03.
An unusually high proportion of politicians are first borns – that is, their parents’ first child. Is this because the first born in a family benefits from the undivided attention of their parents’ resources and expectations? Or is it because the first born develops leadership skills through dealing with their younger siblings?
Rudy Andeweg and Steef Van Den Berg (Leiden University, Holland) questioned 1,200 Dutch individuals due to take office in local or national government. To test the parental vs. sibling theories, they took note of how many politicians were ‘only children’ (without any brothers or sisters) and how many were ‘middle-order children’. 'Only children' would have enjoyed the benefits of their parents’ undivided attention but wouldn't have had any younger siblings to boss around. Middle-order children, by contrast, would have missed out on parental preference, but would have been able to command their younger siblings.
As expected, relative to the general population, they found a greater proportion of politicians were first borns (36 per cent vs. 26 per cent) and fewer were last borns (19 per cent vs. 25 per cent). In support of the parental explanation, they found a disproportionate number of the politicians were only children. Middle-order children, by contrast, were not over-represented among the politicians – undermining the importance of the sibling explanation.
Andeweg, R.B. & Van Den Berg, S.B. (2003). Linking birth order to political leadership: the impact of parents of sibling interaction? Political Psychology, 24, 605-623.
Link to free full-text.
Link to birth order entry on wikipedia.
Note, Alfred Adler wrote a seminal paper on birth order effects in 1928. There’s also another trend among leaders not mentioned by the current study – of the 24 British Prime Ministers between 1809 and 1937, 15 lost one or more of their parents as children. And the pattern continues among modern day leaders: Bill Clinton’s father died before Bill was born, John Major’s father died just before his son’s nineteenth birthday (from Jeremy Paxman's book The Political Animal).