The next year, he habilitated at Ruprecht Karl University of Heidelberg with his thesis "Die Privatangestellten in der modernen Wirtschaftsentwicklung".

In 1931, he succeeded Werner Sombart at the German Faculty for national economy and finance sciences at Humboldt University of Berlin.

As was the case with almost all so-called "Heidelberger economists", Lederer was suspended by the Nazis on 14 April 1933 according to the Gesetz zur Wiederherstellung des Berufsbeamtentums until a final decision would be made.

Lederer, who published the social democratic theory magazine "Die Neue Zeit", was influenced by Karl Marx and Joseph Schumpeter.

He did not support an unregulated free market: he examined the inefficiencies of monopolies, and partially denounced the positive effects of technical progress according to his stagnation theorem.