Demand supply

Agenda
Basics of demand
Closer look at demand
Basics of supply
Closer look at supply

Part 1: Basics of demand

Source: Hyman; Parkin
The law of demand
THE LAW OF DEMAND states that, in general, other things being constant, the lower the price of a good, the greater the quantity of that good buyers will purchase over a given period (and conversely).
More precisely: other things remaining the same, the higher the price of a good, the smaller is the quantity demanded; and the lower the price of a good, the greater is the quantity demanded.

Demand schedule: an example

Demand curve: an example

The law of demand – things to remember
Ceteris paribus qualification
Shift factors of demand
Shift along demand curve and shift of demand curve
Quantity demanded vs. demand
Effective demand vs. potential demand
Time dimension

Ceteris paribus qualification
Recall Alfred Marshall’s concept of „pound”.

Shift factors of demand
SHIFT FACTORS OF DEMAND = the things held constant when plotting demand curve; factors influencing demand (other than price).
Basic shift factors of demand:
income,
prices of other goods (substitutes and complements),
preferences.

Shift factors of demand: an example
Let’s suppose that buyers’ income increases.
At each price they will demand more.

Quantity demanded vs. demand
QUANTITY DEMANDED = amount of a good that buyers are willing and able to purchase over a period at a certain price.
DEMAND = quantity of a good which buyers are willing and able to purchase over a period at various prices.

Effective demand vs. potential demand
WANTED ≠ DEMANDED in the sense we’re using the term
If you demand something, then you:
want it,
can afford it,
plan to buy it.
EFFECTIVE DEMAND = consumers are willing and able to purchase
POTENTIAL DEMAND = consumers are only willing to purchase

Part 2: Closer look at demand

The forces behind the law of demand
SUBSTITUTION EFFECT of a good’s rising price: when the price of a good rises, we will substitute other similar goods for it; the good is now more expensive in relation to other goods; we switch to alternatives.

Money price vs. relative price
MONEY PRICE = the number of dollars that must be given up in exchange for a good.
RELATIVE PRICE = the ratio of price of one good to price of another good.

The forces behind the law of demand (cont.)
INCOME EFFECT of a good’s rising price: when the price of a good rises, we find ourselves somewhat poorer than before; we are not able to afford to buy so much of the good with our money as earlier; purchasing power of our income falls.

Nominal income vs. real income
NOMINAL INCOME = income measured in terms of an amount of money (the number of dollars)
REAL INCOME = income measured in terms of the quantity of goods the money can buy; in other words, it reflects PURCHASING POWER of the money

Relationship between income and demand
From the point of view of the effect changing income has on demand, goods can be categorized into:
normal (superior) goods,
inferior goods.
INFERIOR GOODS: low-quality, often second-hand goods that have more expensive substitutes.
The higher buyer’s income, the lower is demand for inferior goods (because we substitute better goods for them).

Relationship between prices of other goods and demand
From the point of view of the effect prices of other goods have on demand, the goods can be divided into:
substitutes,
complements.
SUBSTITUTES = alternatives, similar goods that can satisfy (better or worse) the same need.
COMPLEMENTS = goods used together in order to satisfy a need.

Shift factors of demand: recapitulation
Outward shift of demand curve can be caused by:
increase in income (normal goods),
decrease in income (inferior goods),
increase in prices of substitutes,
decrease in prices of complements,
change in buyers’ tastes, preferences and habits to the advantage of a good.
Inward shift of demand curve can be caused by:
decrease in income (normal goods),
increase in income (inferior goods),
decrease in prices of substitutes,
increase in prices of complements,
change in buyers’ tastes, preferences and habits to the detriment of a good.

Part 3: Basics of supply

Source: Hyman
The law of supply
THE LAW OF SUPPLY states that, in general, other things being constant, the lower the price of a good, the smaller the quantity of that good sellers will make available in the market over a given period (and conversely).

Supply schedule: an example

Supply curve: an example

The law of supply – things to remember
Ceteris paribus qualification
Shift factors of supply
Shift along supply curve and shift of supply curve
Quantity supplied vs. supply
Effective supply vs. potential supply
Time dimension

Shift factors of supply
SHIFT FACTORS OF SUPPLY = the things held constant when plotting supply curve; factors influencing supply (other than price).
Basic shift factors of supply:
production costs (prices of inputs),
changes in technology,
the state of nature.

Shift factors of supply: an example
Let’s suppose that prices of inputs increase.
At each price sellers will supply less.

Quantity supplied vs. supply
QUANTITY SUPPLIED = amount of a good that sellers are willing and able to deliver in the market over a period at a certain price.
SUPPLY = quantity of a good which sellers are willing and able to deliver in the market over a period at various prices.

Effective supply vs. potential supply
Having the resources and technology is not enough to supply a good.
If a firm supplies a good or service, the firm:
has the resources and technology to produce it,
can profit from producing it,
plans to produce it and sell it.

Part 4: closer look at supply

Forces behind the law of supply
The law of diminishing returns implies that producing every additional unit of a good becomes more and more expensive. To offer more goods, firms must be motivated by rising price.
In other words, it is never worth producing a good if the price received for the good does not at least cover the marginal cost of producing it.