You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Imperialism

Context:
The correlation between capitalism, aristocracy, and imperialism has long been debated among historians and political theorists. Much of the debate was pioneered by such theorists as J. A. Hobson (1858–1940), Joseph Schumpeter (1883–1950), Thorstein Veblen (1857–1929), and Norman Angell (1872–1967). While these non-Marxist writers were at their most prolific before World War I, they remained active in the interwar years. Their combined work informed the study of imperialism and it's impact on Europe, as well as contributed to reflections on the rise of the military-political complex in the United States from the 1950s. Hobson argued that domestic social reforms could cure the international disease of imperialism by removing its economic foundation. Hobson theorized that state intervention through taxation could boost broader consumption, create wealth, and encourage a peaceful, tolerant, multipolar world order.

Question:
When were Joseph Schumpeter and Norman Angell at their most prolific writing period?

before World War I