Answer:
The income effect
Step-by-step explanation:
The income effect is how real income is affected when there is change in price of goods and services.
Assuming income remains constant, as price falls income is able to purchase more goods and services, and as price increases the income will buy less of goods and services.
Also when people earn more they tend to buy more products.
In this case when the economy bis doing well and incomes increase sales of national brand of orange juice rises. The sales of generic orange juice however falls.
This shows that if there is enough money people prefer to by national brand of juice than generic orange juice.