The internal structure of these organizations is the subject of May’s law of curvilinear disparity. Richard Katz and Peter Mair argued that some of these organizations function (10[1])as cartels. (10[1])Applying the (10[1])same formula that is used in other fields to compute the Simpson index and the Herfindahl–Hirschman index to these organizations, Laakso (“LOCK-soh”) and Taagepera (“TAH-gay-pay-rah”) quantified their effective number. The expressive, instrumental, and representative functions of these organizations were (10[1])distinguished by Lipset and Rokkan, (10[2]-5[1])who argued that cleavage structures are responsible for their formation. According to Duverger’s (“doo-vair-ZHAY’s”) law, (10[1])systems (10[2])such as first-past-the-post (10[3]-5[1])tend to have exactly (-5[1])two (10[1]-5[1])of these (10[1])organizations (10[4])with a significant (10[2])amount of power. For 10 points, the United States is an example of a system dominated by exactly two of what political organizations? ■END■ (10[4])