Energy demand is estimated as a function of the energy demand per unit GDP (in PPP terms) and total GDP (in PPP terms), with adjustments related to energy prices and improvements in energy use efficiency.  The energy demand per unit GDP depends on GDP per capita (in PPP Terms).  The improvement in energy use efficiency is a combination of autonomous trend in efficiency of energy use ( enrgdpgr ) and an additional amount that accelerates the improvements for (non-exporting) countries that have efficiencies below the global average.  The price effect takes into account both the domestic and global prices of energy, as well as any carbon tax ( carbtax ).  The user can control the price elasticity of energy demand ( elasde ) and the historical weight used to smooth energy prices ( ehw ).  Finally, the user can also use an energy demand multiplier ( endemm ) to directly modify energy demand.