unemployment and inflation

• If equilibrium level of national income below full employment rate will be excess capacity in economy hence demand deficient unemployment- there will be what is know as a deflationary or recessionary gap
• If full employment level of real income, aggregate expenditure exceeds national income will be excess demand therefore demand pull inflation, involving an inflationary gap. Therefore this must be closed by raising withdrawals or lowering injections
• booms and recessions 

  Why persist- Time lags, bandwagon effects, group behaviour

  Why end- ceilings and floors, echo effects, the accelerator, sentient and expectations, random shocks, changes in government policy