Productivity is a measure of the efficiency of production. Productivity is a ratio of what is produced to what is required to produce it. Usually this ratio is in the form of an average, expressing the total output divided by the total input. Productivity is a measure of output from a production process, per unit of input. The production function is a simple description of the mechanism of economic growth. Economic growth is defined as any production increase of a business or nation (whatever you are measuring). The rapid development in groundwater, however, comes at a price. In many arid areas, more and more areas are in overdraft and the associated water-quality problems are emerging. In India, unreliable power supplies combined with weak management of groundwater resources greatly constrain the growth of irrigated agriculture.