the book that is the basis for modern macroeconomic theory is
Macroeconomics Macroeconomics, at least in its modern form,[26] began with the publication of John Maynard Keynes's General Theory of Employment, Interest and Money.[25][27] When the Great Depression struck, classical economists had difficulty explaining how goods could go unsold and workers could be left unemployed. In classical theory, prices and wages would drop until the market cleared, and all goods and labor were sold. Keynes offered a new theory of economics that explained why markets might not clear, which would evolve (later in the 20th century) into a group of macroeconomic schools of thought known as Keynesian economics â€“ also called Keynesianism or Keynesian theory.