I've read some posts regarding different competitive residencies, and I'm a little puzzled by that. In the data tables for this years match, I found the following data:

Neurological surgery: 43 positions offered, 37 ranked by US grads, 39 ranked by all grads. This leaves 4 positions unfilled, yet it is considered a competitive residency. Why is it so?

Otolaryngology: 42 positions offered, 36 ranked by US grads, 40 ranked by all grads. This leaves 2 positions unfilled, and it is considered very competitive. Again, why is it so?
Is it because so many of the positions are ranked by US grads, or what? Since there are more positions being offered than ranked, I would think that there would be more graduates who applied for these residencies.

My last question is this: Is urology considered a competitive residency?
The facts for urology are: 50 positions offered, 44 ranked by US grads, 52 ranked by all grads.

Thanks for Your answers.