In the table above, each class of supply has a consumer. Some classes of supply have a linear demand relationship - as more troops are added more supply items are needed - as more equipment is used more fuel and ammo is consumed. Other classes of supply must consider a third variable besides usage and quantity: time. As equipment ages more and more repair parts are needed over time, even when usage and quantity stays consistent. By recording and analyzing these trends over time and applying to future scenarios, the US Military can accurately supply troops with the items necessary at the precise moment they are needed.[18] History has shown that good logistical planning creates a lean and efficient fighting force. Lack thereof can lead to a clunky, slow, and ill-equipped force with too much or too little supply.