Energy efficiency is an important factor in an economy, since it helps meet energy needs, decrease costs, and lower environmental impacts. A review of the evolution of energy intensity in European and Former Soviet Union countries indicates a positive trend: high-energy-intensity countries have now reached the level of medium-energy-intensity economies 15 years earlier, and in the same period, medium-energy-intensity ones had similarly evolved to levels of low-energy-intensity. At the same time, the fast transitioning economies of Central Europe converged towards similar levels of energy...