Sturgeon’s Law

“90% of everything is crap.”

That’s a paraphrase of:

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 SF is crud. Using the same standards that categorize 90% of science fiction as trash, crud, or crap, it can be argued that 90% of film, literature, consumer goods, etc. is crap. In other words, the claim (or fact) that 90% of science fiction is crap is ultimately uninformative, because science fiction conforms to the same trends of quality as all other artforms.

— Theodore Sturgeon

Counter-intuitive because most people only see at most the top 10-15% of output from any given creative field.

And the inverse:

The inverse is obviously also true: if ninety percent of everything is crap, then even in areas that are generally considered inferior (such as soap operasdime novels or fan fiction), there must be ten percent that may be worth something.

— Various Wikipedia editors working asynchronously

From Wikipedia.