Which of the following factors would NOT shift the demand curve?

The demand curve represents the relationship between the price of a good and the quantity demanded by consumers. Factors that shift the demand curve include changes in consumer income, the price of related goods (substitutes and complements), and consumer preferences.

In this context, a change in taxation policy is not a direct factor that shifts the demand for a particular good. Instead, it can influence other factors such as consumer income or overall spending power, but it does not directly change the demand for a specific product like the other options. An increase in consumer income would typically lead to an increase in demand for normal goods, and a decrease in the price of a complementary good would make the related product more attractive, thereby increasing demand. Similarly, changes in consumer tastes and preferences can shift demand explicitly as they affect how much of the product consumers want to buy at any given price.

Thus, while taxation policy has implications for consumers and market conditions, it does not straightforwardly alter the demand for a specific good, making this the correct identification of a factor that does not shift the demand curve.