Established by the Greeks, Romans, and Arabs, systematic learning began paying great dividends with new discoveries in technology and farming that opened the door to the agricultural revolution. The rise in monasteries, libraries, and universities guaranteed that new discoveries spread - opening the way for a population and economic boom lasting several hundred years. This period brought the horse harness, the mould-board plow, and the powered loom into widespread use. As a result, crop yields shot up, and cloth prices dropped dramatically, feeding a commercial expansion that swept through the world.