I just bought a woman's babies from an albinoXalbino litter and there were 17!

I just had an albinoXcolored litter of 14!

My colored rats (eating the same food, on the same bedding) are having 6-8 babies at a time.

ONE colored group gives me consistently 10-12 at a time.

I definitely think it has most to do with the lines. If you breed from lines that consistently have larger litters, you will probably continue to have larger litters. And since feeder breeders, pet shop breeders, etc want MORE MORE MORE babies, they will be doing just that, breeding for LARGER litters. They probably just started with albinos and kept going.

Plus, maybe labs like the "clean look" of the white rats because they can see any imperfections on them easier. And labs also like large litters I'm assuming