Production efficiency is usually assumed in microeconomic theory. In particular, a single production function is supposed to exist for all producers in the industry. Output may be random due to variation in the levels of uncontrollable inputs (e.g. weather in agricultural production; power failures in industry); however expected value of output is identical for decision-makers using the same input bundle. Further, in general it is assumed that producers equate marginal rates of transformation (either factor-factor, factor-product or product-product) to relevant price ratios. That is, costs are minimized and profits are maximized given the technology available at a point in time. Assuming absence of waste is convenient for understanding the workings of the price system; However, it appears to be overly restrictive for micro (and particularly management) oriented inquiries.