IFs distinguishes between ultimate resources and reserves, where the latter represent the amount of energy actually discovered and available for production. Ultimate resources are initially determined in the pre-processor, but the user can override these estimates using either absolute values ( resor , resoruncon ) or multipliers ( resorm , resorunconm ). There is also a parameter controlling the portion of unconventional oil that is economic to produce ( enresorunce ). For non-renewable energy types, i.e., fossil fuels, reserves increase with discoveries and decrease with production. The rate of discovery includes a base rate ( rdi ) and an annual increment ( rdinr ). There are further adjustments related to the world energy price, the remaining resources, and the current rate of production. The user can control the effect of world prices on discovery ( elasdi ) and can also intervene with a discovery multiplier ( rdm ).