Demand in a market can change for many reasons, As it does so , the market responds by altering supply. This happens spontaneousty - there is no need for a guiding hand or plan in a market that encourages competition among self-interested people./
During a rainy summer./
demand for umbrellas soars./
As prices rise, so do profits./
Umbrella firms employ more people and enjoy profits until other firms enter the market, forcing prices back to a "natural level"./
Staff go to work in the booming umbrella business./
Self-interested employers let go of staff./
As prices drop, so do profits./
demand for sunglasses drops.