instruction:
This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
question:
Passage: One philosophical school which has historically had a close relationship with process philosophy is American pragmatism. Whitehead himself thought highly of William James and John Dewey, and acknowledged his indebtedness to them in the preface to Process and Reality. Charles Hartshorne (along with Paul Weiss) edited the collected papers of Charles Sanders Peirce, one of the founders of pragmatism. Noted neopragmatist Richard Rorty was in turn a student of Hartshorne. Today, Nicholas Rescher is one example of a philosopher who advocates both process philosophy and pragmatism.
answer:
 What pragmatists did Whitehead not acknowledge in the preface to "Process and Reality"?


question:
Passage: It is not clearly documented when the title of the Grand Duke was first introduced, but the importance of the Kiev principality was recognized after the death of Sviatoslav I in 972 and the ensuing struggle between Vladimir the Great and Yaropolk I. The region of Kiev dominated the state of Kievan Rus' for the next two centuries. The Grand Prince ("velikiy kniaz'") of Kiev controlled the lands around the city, and his formally subordinate relatives ruled the other cities and paid him tribute. The zenith of the state's power came during the reigns of Vladimir the Great (980–1015) and Prince Yaroslav I the Wise (1019–1054). Both rulers continued the steady expansion of Kievan Rus' that had begun under Oleg.
answer:
When was the title of Grand Duke introduced?


question:
Passage: Plotting the relationship between level of income and inequality, Kuznets saw middle-income developing economies level of inequality bulging out to form what is now known as the Kuznets curve. Kuznets demonstrated this relationship using cross-sectional data. However, more recent testing of this theory with superior panel data has shown it to be very weak. Kuznets' curve predicts that income inequality will eventually decrease given time. As an example, income inequality did fall in the United States during its High school movement from 1910 to 1940 and thereafter.[citation needed] However, recent data shows that the level of income inequality began to rise after the 1970s. This does not necessarily disprove Kuznets' theory.[citation needed] It may be possible that another Kuznets' cycle is occurring, specifically the move from the manufacturing sector to the service sector.[citation needed] This implies that it may be possible for multiple Kuznets' cycles to be in effect at any given time.
answer:

During what time period did income inequality increase in the United States?