“ all else remaining the same” or “other things being equal”
Relative prices and Money Prices
Money Price is the price that is observed in terms of today’s dollars.
Relative price is the price of good or service in terms of another. It is the money price of one commodity divided by the money price of another; the number of units of one commodity that must be sacrificed to purchase one unit of another commodity.
The good with an upward demand curve is called “Giffen Good”, but it rarely exits in the real world.
Whether luxury goods are Giffen Goods? Some people say that in certain circumstances, only when the prices of some goods, such as luxury goods, are high, they tend to be willing to buy it. When the prices are low, they will not buy it.
If a sufficient number of demanders expect the price of the good to increase in the future, these people will increase their demand for the product today in order to stock up on the good and avoid the higher price in the future. If a sufficient number of demanders think the price will decline tomorrow, the demand today will decrease.
Expectation of a rise in income may cause consumers to purchase more of normal goods today at current prices.
Supply is the relationship between the price of a good and the quantity supplied by producers.
A market supply is found by adding up individual producer supply schedules. Summing the quantity supplied at each price by each producer (horizontal summing of the individual supply curves) derives the market supply curve.