There is a difference between demand and desire. A sickly child needs a tonic or a peon desires to have a TV set. But, this kind of need and desire do not constitute demand.
When a person is willing and able to pay for what he desires, then the desire is changed into demand.
The three components are needed to constitute any demand for a commodity.
1. Desiring to have a commodity
2. Financial ability or able to pay for a commodity
3. Willing to pay for the commodity
Types of Demand
There are three 3 kinds of demand.
1. Price demand
Price demand refers to the various quantities of a commodity or service that a consumer would purchase at a given time in a market at various hypothetical prices. Other things remain unchanged, like; consumers’ taste and preference, income, prices of inter-related goods. Price demand expresses the relationship between prices and quantities demanded.
2. Income Demand
Income demand refers to the various quantities of goods and services, which would be purchased by the consumers at various levels of incomes. Other things remain ‘unchanged. Income demand expresses the relationship between income and quantities demanded.
3. Cross Demand
The cross demand means the quantities of a commodity or service which will be purchased with reference to change in price not of this goods but of other inter-related goods.
These goods must be either substitute or complementary.
Which goods are substitute or complementary. A change in price of tea may affect the demand for coffee. Similarly, if horses become cheap, demand for carriages may increase.
You can see more article about Agricultural Economics
Important Agricultural Websites
Online Agricultural Study
Food and Agricultural Organization
United States Department of Agriculture