Ken-Ichi Inada
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Ken-Ichi Inada (1925 Gunma Prefecture, Japan; ʈ May 17, 2002) was a Japanese economist.
Beginning in the 1950s, Professor Inada wrote a number of important papers on welfare economics, economic growth and international trade. His contributions include an early extension of Kenneth Arrow's impossibility theorem on the existence of a social welfare function (1955). Professor Inada's extension of the Stolper-Samuelson theorem to the many-good, many-factor case is also considered as a classic piece in trade theory (1971).
Professor Inada has taught at universities including Osaka University and Tokyo Metropolitan University, served as a member of the honorary board of editors for the Japanese Economic Review since its first publishing in 1995, as well as being elected president of the Japanese Economic Association in 1980.
He is known for the Inada conditions on a production function that can guarantee the stability of an economic growth path in a neoclassical growth model. The six conditions are:
- the value of the function at 0 is 0,
- the function is continuously differentiable,
- the function is strictly increasing in x,
- the derivative of the function is decreasing (thus the function is concave),
- the limit of the derivative towards 0 is positive infinity,
- the limit of the derivative towards positive infinity is 0.
