supply-demand relationship
Economic term referring to the balance or interaction between supply and demand in a market.
The supply-demand relationship for crude oil is affecting prices.
需給関係 is a more formal, compound noun often used in economic analysis, while 需要と供給 is a more explicit phrase meaning 'supply and demand'.
Compound of 需給 (supply and demand) and 関係 (relationship). The exact historical derivation is uncertain, but the term is a standard modern economic expression.