The starting point in any type of competition analysis is the definition of the "relevant" market. There are two fundamental dimensions of market definition: (i) the product market, that is, which products to group together; and (ii) the geographic market, that is, which geographic areas to group together. Market definition takes into account both the demand and supply considerations. On the demand side, products must be substitutable from the buyer’s point of view. On the supply side, sellers must be included who produce or could easily switch production to the relevant product or close substitutes.