145Fourthly, as regards the existence of a distortion of competition in the common market, it should be borne in mind that, according to settled case-law, while the Commission must at the very least refer to the circumstances in which aid was granted in the statement of the reasons for its decision where those circumstances show that the aid is such as to affect trade between Member States and to distort or threaten to distort competition, it is not required to carry out an economic analysis of the actual situation on the relevant markets, of the market share of the undertakings in receipt of the aid, of the position of competing undertakings or of trade flows between Member States. Furthermore, in the case of aid granted illegally, the Commission is not required to demonstrate the actual effect which that aid has had on competition and on trade between Member States. If that were the case, such a requirement would ultimately give Member States which grant unlawful aid an advantage over those which notify the aid at the planning stage (see, to that effect, Case T-55/99CETM v Commission [2000] ECR II-3207, paragraphs 100, 102 and 103; Case T-152/99HAMSA v Commission [2002] ECR II-3049, paragraph 225; and Case T-198/01Technische Glaswerke Ilmenau v Commission [2004] ECR II-2717, paragraph 215).