NimT's dashboard

If I have film A, ranked at #90 on my list, and film B, ranked at #100, and I choose film A, then what effect does this have on my overall list?

It seems to me that such choices make up 80% of the rankings that I am asked to make, but they seem to have no effect on my overall list. I've made over 1000 rankings, but my list still hasn't really taken shape, because too many of them are these apparently meaningless choices between films that are already ranked in the correct order (even if they are both too low or too high on the list).