The portion of output that is not explained by measured quantities of inputs into the production process. TFP (also called multi-factor productivity) is usually interpreted as a measure of the level of technology, so an increase in TFP reflects technological advance. For example, if the production function is Cobb–Douglas with output, Y, related to capital, K, and labour, L, by Y = AK^α‎ L^β‎, then A is the value of TFP. The rate of growth of TFP (the growth rate of technology) is measured by the Solow residual, under the assumption of competition in factor markets.