externalities lead to greater responses inefficiency because a market will ignore cost or benefits imposed on third parties by activity in that market. inefficiency because a market will ignore cost or benefits imposed on third parties by activity in that market. efficiency in markets because the market includes only cost and benefits imposed directly on the businesses only. efficiency in markets because the market includes only cost and benefits imposed directly on the businesses only. efficiency in markets because a market will include cost or benefits imposed on third parties by activity in that market. efficiency in markets because a market will include cost or benefits imposed on third parties by activity in that market. inefficiency in markets because a market will include cost or benefits imposed on third parties by activity in that market.