I've seen a few studies that when taken together aren't super conclusive, but suggest that perhaps around 3/4 of cats have handedness and that there may be some bias to one side or the other based on sex.

See my comment just above yours!

i've seen a study (which i can't find) that boy cats are usually lefty and girls righty. that fits our sample size of four, interestingly, and perhaps randomly, since i can't find the study.