Renewable energy resources are unevenly distributed across India. Commercially viable wind power capacity was the first to be developed on a large scale in the 1990s, mostly in the western and southern states, thanks to the incentive of accelerated depreciation (AD) that the government offered. (AD is an income tax benefit which allows faster depreciation of assets, reducing the tax burden. In the case of renewable energy, AD rate was 100% earlier, and has now been reduced to 40%. This compares favourably with other machinery, which depreciates at a 15% rate.)