Shift in Demand Curve

Examples of When Demand Changes No Matter the Price

demand curve shift
••• When a determinant of demand other than price changes, the entire demand curve shifts.

A shift in the demand curve is when a determinant of demand other than price changes. Here are these other four determinants.

  1. Income of the buyers.
  2. Consumer trends and tastes.
  3. Expectations of future price, supply, needs, etc.
  4. The price of related goods. These can be substitutes, such as beef versus chicken. They can also be complementary, such as beef and Worcestershire sauce.

There is a fifth determinant that applies to aggregate demand only.

That is the number of potential buyers.

The demand curve plots the relationship between the quantity demanded of a good or service and its price. The curve depicts in a graphical way the demand schedule, which details exactly how many units will be bought at each price. The law of demand guides that amount. That says less is bought at a higher price ceteris paribusThat means all determinants of demand other than price must stay the same.

Factors That Cause a Demand Curve to Shift

A demand curve shifts when a determinant other than prices changes. If the price changes, then the  demand curve will tell you how many units will be sold. But if the price remains the same, and the income changes, then that changes the amount purchased at every price point. People can buy more of what they want when they have more income. Of course, the seller will probably raise the price at some point, causing inflation.

But at least in the short-term, the price will remain the same and the quantity sold will increase.

The same effect occurs if consumer trends or tastes change. If people buy electric vehicles, but the price of gas stays the same, then less gas will be sold. 

The curve shifts to the left if the determinant causes demand to drop.

That means less of the good or service is demanded at every price.  For example, when the economy is booming, buyers' incomes will rise. That means they'll buy more of everything, even though the price hasn't changed. 

The curve shifts to the right if the determinant causes demand to increase.  That means that more of the good or service are demanded at every price. Using that same illustration, when the economy is in a recession, buyers' income drops. They will buy less of everything, even though the price is the same.

Examples

Income of the buyers: If you get a raise, you're more likely to buy more of both steak and chicken, even if their prices don't change. That shifts the demand curves for both to the right.

Consumer trends: During the mad cow disease scare, consumers preferred chicken over beef. Even though the price of beef hadn't changed, the quantity demanded was lower at every price. That shifted the demand curve to the left.

Expectations of future price: When people expect prices to rise in the future, they are more likely to buy more of a good now, even if the price hasn't even changed. In other words, they want to stock up now before prices rise. That shifts the demand curve to the right.

That's why the Federal Reserve sets up an expectation of mild inflation. Its target inflation rate is 2.0 percent. 

The price of related goods: If the price of beef rises, you're more likely to buy more chicken. Even if its price doesn't change. That's how an increase in the price of a substitute (beef) shifts the demand curve to the right for chicken. The opposite occurs with the demand for Worcestershire sauce, a complementary product. Its demand curve will shift to the left as you are less likely to buy it at any price since you have less beef to put it on. 

The number of potential buyers (affects aggregate demand only): When there's a flood a newly eligible consumers in a market, they will naturally buy more product at the same price, shifting the demand curve to the right. That happened when standards were lowered for mortgages in 2005.

Suddenly, people who hadn't been eligible for a home loan could get one with no money down. More people bought homes until the demand outpaced supply.  At that point, prices rose in response to the shift in the demand curve.