Lower demand would be a shift from D2 back to D1 on this chart: https://en.wikipedia.org/wiki/Supply_and_demand#/media/File:Supply-and-demand.svg https://en.wik

Lower demand would be a shift from D2 back to D1 on this chart: https://en.wikipedia.org/wiki/Supply_and_demand#/media/File:Supply-and-demand.svg https://en.wikipedia.org/wiki/Supply_and_demand#/media/File:... But if the demand curve shifts leftwards or downwards enough, it won't intersect with the supply curve at all. At that point, the model says commerce halts because there's no price that both sellers and buyers are willing to trade at.