Was indeed Heinlein (Goodreads link):
Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded—here and there, now and then—are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty.
This is known as "bad luck.”
This is from "Notebooks of Lazarus Long""Notebooks of Lazarus Long" by Robert A. Heinlein, in Analog Science Fiction/Science Fact, June 1973Analog Science Fiction/Science Fact, June 1973, p. 77.