Double take: Oliver and James as the Weasley twins in the 2003 film Harry Potter And The Prisoner Of Azkaban surrounded by their co-stars. Identical: James, left, and Oliver Phelps arrive at London's Odeon Leicester Square for the world premiere of 'Harry Potter and the Chamber of Secrets' in 2002.
An increase in demand is represented by a shift of the demand curve to the right: A decrease in from ECON 101 at Universitat Pompeu Fabra
A demand curve can shift to the left for a wide variety of reasons. A negative product review can reduce consumer demand for an item, shifting the demand curve to the left. Similarly, a government health warning about an item also can reduce demand and shift the curve.