How small do Skechers shoe sizes come in?

I have owned several pairs of skechers. i measure a size 6 so i bought my first pair in a 6 & found they were too small. The next pair I bought was the same deal. i figured they'd stretch a little but they didn't. When i measured my foot with skechers online foot measurer i found that according to them i am actually a 6.5. The 3rd pair i bought in a 6.5 & they fit perfectly. so i would say they run a half a size too small.