Index numbers are not directly measurable, but represent relative changes
Present use of index numbers
Measuring trends in a wide variety of areas such as stock market prices, cost of living, industrial and agricultural production, changes in exports and imports etc.
Index numbers are one of the most used statisticaltools in Economics
Index numbers were originally developed to measure changes in the price level
Index number
A device to measure changes in an economic variable (or group of variables) over a period of time
Economic variable
A variable that is affected by economic conditions
Original use of index numbers
Measuring changes in the price level
Marginal utility is the amount of extra pleasure or satisfaction derived from consuming one more unit of a product.
The law of diminishing marginal utility states that additional units of a good will yield less satisfaction than previous units.
Substitution effect refers to the change in quantity demanded as a result of a price change, holding constant all other factors that affect demand.