however as with any subsidy instrument careful design and periodic recalibration are necessary to ensure that objectives are achieved at the lowest cost to society and this requires strong government capacity regulatory capture where entrenched industry interests are able to extract subsidies even after the legislative objective has been attained is common yet energy technology change has slowed considerably at the level of the global fuel mix since the s and there is no evidence to support the popular notion of an acceleration of energy technology change either at the fuel or at the sector plant or unit levels