Even then, some policies take years to show an impact - often with amplification or diminution based upon other events that occur long after a President is gone

Even then, some policies take years to show an impact - often with amplification or diminution based upon other events that occur long after a President is gone. Look at how long it took for the housing market bubble to grow before bursting - 15 to 30 years, depending upon which policies you view as being contributing factors.