DEMAND

Demand is the willingness of consumers to buy a product at various price levels over a period of time. In short demand is the large number of items requested on a specific market with a specific price level at a certain income level and within a certain period.Factors affecting demand:
1. Price of the item itselfIf the price of the goods getting cheaper, the demand for goods is increasing.
2. Prices of goods and other relatedEffect if there are 2 items interrelated nature interrelationships substitution (replacement) and is the complement (penggenap).
3. The level of income per capitaMay reflect purchasing power. The higher the income level, the stronger purchasing power, thus demand for a product increases.
4.Selera or habitThe level of demand is determined by the tastes or habits of a community lifestyle.
5.Jumlah residentsThe more the number of people who have a desire or habit of the need for a particular item, the greater the demand for the goods.
6.Perkiraan future priceIf we estimate that the price of a good goes up, it is better to buy the item now, thus encouraging people to buy more at this time in order to reduce spending in the future.
7.Distribusi revenueThe level of income per capita could give the wrong conclusion when bad income distribution. If bad income distribution, meaning the general purchasing power weakened, so the demand for a product decreases.
8.Usaha-venture manufacturers increase sales.Persuasion of the seller to buy a huge role in influencing society. Promotional efforts to the buyer often encourage people to buy a lot more than usual.
Law of DemandThe law of demand is essentially a hypothesis which states:"The relationship between the quantity demanded at a price of goods in which the inverse relationship when the price increases or increased the quantity of goods demanded will decrease, and vice versa if the number of goods increases the price down."
Demand CurveDemand curves can be defined as:"A curve that describes the nature of the relationship between the price of a particular item by the number of goods that the buyer requested." Demand curve for different types of goods generally decreases from left to bottom right. Such curves are caused by the nature of the relationship between price and quantity demanded which have an inverse relationship properties.

Demand Theory, to stated:"Comparison straight between the demand for that price if demand increases, the relative prices will rise, whereas if demand falls, then the relative price will fall."

(http://keripiku.blogspot.com/2012/03/teori-permintaan-dan-penawaran-serta.html)