In one of the few studies to empirically investigate narcissistic traits in politicians, Robert Hill and Gregory Yousey administered the NPI to 123 university faculty, forty-two politicians (state legislators from four states), ninety-nine clergy (both protestant ministers and Catholic priests), and 195 librarians. Their 1998 study found a statistically significant difference in total scores, with politicians scoring higher than the other three professional groups. In terms of the four subscales, politicians scored the highest on the leadership/authority subscale, and clergy scored the lowest on the exploitativeness/entitlement subscale.

In other words, politicians did score higher than the other three groups in total narcissism, but the differences seemed mainly due to their high scores on the leadership/authority scores. Interestingly, although the differences did not reach statistical significance, politicians also had the highest scores on superiority/arrogance and exploitativeness/entitlement subscales and professors had the highest scores on self-absorption/self-admiration. Without statistical significance, however, these last differences could be due to chance.