Complex sentence: The Keynesian view of the economy was dominant from the late 1930's until the early 1970's, when Keynes' original idea were elaborated upon, clarified and made more precise.
Split into simpler sentences: The Keynesian view of the economy was dominant from the late 1930's until the early 1970's. During this time Keynes' original ideas were elaborated upon, clarified and made more precise.