Which of the following could cause the market demand curve for guacamole to shift leftward (indicating a decrease in demand)?

• A. An increase in the price of tortilla chips, a complement to guacamole
• B. A decrease in consumer income, assuming guacamole is a normal good
• C. A successful advertising campaign promoting guacamole
• D. A decrease in the price of salsa, a substitute for guacamole

Answer: (B)

Verified step by step guidance

1. Step 1: Understand that a leftward shift in the market demand curve means a decrease in demand at every price level, not just a movement along the curve due to price changes.
2. Step 2: Identify the effect of changes in related goods: an increase in the price of a complement (like tortilla chips) typically decreases demand for the related good (guacamole), potentially shifting demand leftward.
3. Step 3: Consider the impact of consumer income: if guacamole is a normal good, a decrease in consumer income reduces demand, causing the demand curve to shift leftward.
4. Step 4: Analyze the effect of advertising: a successful advertising campaign usually increases demand, shifting the demand curve rightward, not leftward.
5. Step 5: Evaluate substitutes: a decrease in the price of a substitute (like salsa) makes the substitute more attractive, reducing demand for guacamole and shifting its demand curve leftward.