Complex sentence: The Keynesians of the 1950s and 60s had adopted the view that monetary policy does not impact aggregate output or the business cycle based on evidence that, during the Great Depression, interest rates had been extremely low but output remained depressed.
Split into simpler sentences: The Keynesians of the 1950s and 60s had adopted the view that monetary policy does not impact aggregate output or the business cycle. They based this belief on evidence that, during the Great Depression, interest rates had been extremely low but output remained depressed.