I don't think it's surprising that department emails generated no hires. People who take internship opportunities from emails they receive are usually too lazy to look themselves, which probably shows a lack of drive. I say usually, because this isn't always true.

I love these stats though... Would make great presentation material on the importance of being active in a job search. Especially the part about what times to apply... if it's a rolling recruiting basis (which I'm assuming almost every company does), those would probably be advantageous times.