Effects of simultaneous changes in demand and supply - U.S. Postal Service Assume that the wages of postal workers have increased, and at the same time, many people have begun to communicate and pay bills online instead of using regular mails. Hence, the effect of a decrease in demand along with a decrease in supply is a(n) a (n) _____ in price. Therefore, the effect on price of the decrease in demand and decrease in supply is unless we know the sizes of the changes. or decrease, decrease, some change, uncertain increase, decrease, some change, uncertain increase, decrease, no change, uncertain increase, increase, no change, uncertain