NSH is the General Partner which holds NS Limited Partner. The theory of the relationship is that the GP gets a high percentage of the earnings (distribution increase), and in the normal historical market, should yield about 1/3 less. If you look at the distributions and percentage increases NSH vs NS's - you will see NSH got a bigger increase percentage wise.

Lately - I am a fan of the GP's. Find some other GP to LP relationship stocks and let me know. Good luck