In an economically efficient market the total quantity produced is the amount at which the highest price that any buyer would pay for one more unit is equal to the lowest price that any seller would produce that last unit for. If the production level is higher or lower than this efficient level of output then we have an output level inefficiency. If the output level is higher or lower than the efficient level due to some market imperfection like fixed prices, fixed output, market power of sellers or buyers, taxes, tariffs etc. then value is destroyed. The destroyed value is then known as deadweight loss.