Ques: How can we make comparisons between the cost of a product in two different periods if salaries and cost of living may have changed?

Ans: The average income is published in government statistics. The figure can be divided by the average number of hours worked. This gives an income rate per hour. Divide the cost of an item by this rate and it gives the number of minutes an average worker had to work in order to purchase the item. If you compare these figures over time you will see that the number on minutes needed to purchase a television set in the year 2000 is significantly less than any previous period.