Complex sentence: The results imply that oil prices were entirely responsible for the recession; however, Hamilton himself acknowledged that this was probably not the case but maintained that it showed that oil price increases made a significant contribution to the downturn in economic growth.
Split into simpler sentences: The results imply that oil prices were entirely responsible for the recession. Hamilton acknowledged that this was probably not the entire cause but maintained that it showed that oil price increases made a significant contribution to the downturn in economic growth.