Summary
Highlights
The video begins by recapping factors typically held constant when moving along a single demand curve, including the price of related goods and price expectations of the good itself. When these factors change, the entire demand curve shifts.
Income is introduced as a factor that, when changed, shifts the demand curve. An increase in income generally leads to an increase in demand (the curve shifts right) for 'normal goods,' meaning at any given price, more quantity will be demanded. Conversely, a decrease in income typically decreases demand (shifts left). The video notes that this isn't always the case for 'inferior goods,' which will be discussed later.
Population is another factor influencing demand. An increase in population usually leads to an increase in demand, as more people mean more potential buyers at any given price point, shifting the demand curve to the right. A decrease in population would decrease demand, shifting the curve to the left.
Finally, preferences (tastes) are discussed. If consumer tastes or preferences for a product increase, the demand curve shifts to the right, as more people are willing to buy the product at any given price. Conversely, if preferences decrease, demand goes down, and the entire curve shifts to the left. An example of a book's author gaining popularity or having a scandal illustrates this point.