In a real system of levers, wheels, or pulleys, the ama is less than the ima because

In a real system of levers, wheels, or pulleys, the AMA is less than the IMA because of friction. 
AMA (Actual mechanical advantage) is found by dividing output force by effort force. The actual mechanical advantage will always be less than the ideal mechanical advantage. The ideal mechanical advantage assumes perfect efficiency which doesn't account for friction, while actual mechanical advantage does. Therefore; the IMA is always greater than the actual mechanical advantage because all machines must overcome friction.