I have found it helpful to rate each "instance" with my SO based on the rating system used here for escorts (1 - 10)
This histroical data can be used very nicely in spotting trends with charts & graphs.

While with your SO, do you keep your pencil behind your right ear or your left ear?

right

She knows I'm measuring her performance against the model now.  (people seem to step up and do better when they know this)   Last night in the sack she pulled a solid 7, up from the 4's and 5's she had been doing!