Nicholas August Ludwig Jacob Johansen (1844–1928) was a German-American amateur economist, today best known for his influence on and citation by John Maynard Keynes.
He was largely unrecognized in his lifetime, but following the Keynesian Revolution, he was recognized as one of the most significant influences on The General Theory, and he is cited in Keynes's 1930 Treatise on Money (p. 90).
He is credited with devising an early form of effective demand, independent discovery of the multiplier, and less recognized contribution to monetary economics and business cycle theory; (Arestis & Sawyer).
His 1903 Der Kreislauf des Geldes und Mechanismus des Sozial-Lebens (The Circuit Theory of Money, written in German) can be seen as an early work in monetary circuit theory.
In his last years (1928), he warned of an upcoming long period of stagnation, which may be seen as prophesying the Great Depression.