PED stands for Price Elasticity of Demand. It refers to the percentage change of quantity demanded (Qd) of a product as a result of a change in price (P) of that product. It is calculated by dividing the percentage change in Qd by the percentage change in P.PES stands for the Price Elasticity of Supply. It refers to the percentage change of quantity supplied (Qs) of a product as a result of a change in price (P) of that product. It is calculated by dividing the percentage change in Qs by the percentage change in P.YED refers to Income Elasticity of demand, although it doesn't stand for it. In other words it's the percentage change of quantity demanded (Qd) of a product as a result of a change in a consumer's income (Y). It is calculated by dividing the percentage change in Qd by the percentage change in Y.XED refers to Cross Price Elasticity of Demand. It's the percentage change of the quantity demanded (Qdx) of one product (x) as a result of a change in price (Py) of another product. It is calculated by dividing the percentage change in Qdx by the percentage change in Py.