… if there is an oversupply of herring on a given day, the shrewd fishmonger will lower his price …
oversupply
/ˈō-vər-sə-ˌplī/
noun
an excessive supply : an amount of something (such as a good) that is more than is needed or wanted
verb
to supply (something, such as a commodity) in excess : to provide (someone or something) with more than is needed or wanted
The OPEC nations have been oversupplying crude oil for more than two years, seemingly in an attempt to drive their main competitors—US shale oil and gas producers—out of business.