“90% of everything is crap.”

Venture Science Fiction (March 1958) The original expression of this has often been declared to have been "Sure, ninety percent of science fiction is crud. That's because ninety percent of everything is crud." According to Philip Klass Sturgeon made the remark during a talk at New York University around 1951. It has also commonly appeared in variant forms such as "Ninety percent of everything is crap" and is often referred to as "Sturgeon's Law" — though he himself gave that title to another phrase:
Variant: Ninety percent of everything is crud.
Context: I repeat Sturgeon's Revelation, which was wrung out of me after twenty years of wearying defense of science fiction against attacks of people who used the worst examples of the field for ammunition, and whose conclusion was that ninety percent of it is crud.
The Revelation: Ninety percent of everything is crud.
Corollary 1: The existence of immense quantities of trash in science fiction is admitted and it is regrettable; but it is no more unnatural than the existence of trash anywhere.
Corollary 2: The best science fiction is as good as the best fiction in any field.