Final answer:
A shift from demand curve D1 to D2, as described, indicates a decrease in demand, which means that consumers are willing to purchase less of the good at each price point.
Step-by-step explanation:
When analyzing demand curves, a shift from D1 to D2 typically corresponds to a change in the level of demand, not just the quantity demanded at a particular price. If a demand curve shifts from Do to D1, it indicates an increase in demand. Conversely, if the demand curve shifts from Do to D2, it signifies a decrease in demand. This change in demand means that for any given price, consumers are willing to buy more or less of the good, leading to a new demand curve.
Therefore, beginning on demand curve D1, a shift to demand curve D2 would indicate a(n) decrease in demand. This is because the entire curve has shifted to the left, representing a situation where at each possible price point, consumers are now willing to purchase a smaller quantity of the good, which is the definition of decreased demand.