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	Törnqvist Index	Growth Accounting
Field	Economics	Economics
Family	Process / pipeline	Regression model
Year of origin	1936	1957
Originator	Leo Törnqvist; superlative theory by W. Erwin Diewert	Robert Solow; Dale Jorgenson & Zvi Griliches
Type	Superlative index number for aggregating prices or quantities	Production-function-based decomposition of output growth
Seminal source	Diewert, W. E. (1976). Exact and superlative index numbers. Journal of Econometrics, 4(2), 115–145.	Solow, R. M. (1957). Technical change and the aggregate production function. The Review of Economics and Statistics, 39(3), 312–320.
Aliases	Tornqvist Index, Tornqvist-Theil Index, Translog Index, Tornqvist Price Index	Sources of Growth Analysis, Solow Growth Accounting, Production Function Decomposition, Total Factor Productivity Accounting
Related	3	3
Summary	The Törnqvist index is a superlative index number used to aggregate many individual prices or quantities into a single measure of overall price change or quantity change between two periods. It is a weighted geometric mean of the individual price (or quantity) relatives, where each item's weight is the average of its value shares in the two periods. Because it is 'exact' for the flexible translog aggregator function, it is the standard tool for constructing productivity indices and is widely used in national accounts, productivity statistics, and price measurement.	Growth accounting is a production-function-based framework that decomposes the growth rate of aggregate output into the contributions of growth in measured inputs — typically capital and labour — and a residual that captures the growth in total factor productivity (TFP). Building on Robert Solow's 1957 derivation and refined by Dale Jorgenson and Zvi Griliches in 1967, it weights each input's growth rate by its share of national income and attributes whatever output growth is left unexplained to improvements in productivity, technology, and efficiency.