Option 2: 1930s -> Macroeconomics emerged as a separate subject in the 1930s, primarily due to John Maynard Keynes' groundbreaking work "The General Theory of Employment, Interest and Money" published in 1936. This book was written during the Great Depression and introduced revolutionary concepts about aggregate demand, unemployment, and government intervention in the economy. Keynes' work distinguished macroeconomics (study of the economy as a whole) from microeconomics (study of individual markets), establishing it as an independent field of economic study. -> correct