As described in The_3_I's interests, ideas, and institutions interact in International Political Economy theories. This post will explore the role of interests and analyze the theories particularly pertaining to interests. In order to further understand the interplay between the 3 I's of IPE be sure to see the other post.
Historically, Adam Smith was one of the first major proponents of the importance of ideas in IPE. He believed that Britain's foreign economic policy was derived from the influence of interest groups in determining policy. He believed that mercantilists and special interest groups had reduced the mobility of goods much more than the politicians such as kings and queens. A contemporary scholar that has followed in Smith's footsteps in Ronald Rogowski. The link will take to you a detailed description of Rogowski's updated version of Special Interests role in IPE.
Interests form when groups of people are motivated by a single purpose to increase wealth, power, status, or any other political, economic, or social interest. In specific, IPE interests focus on both economic and political power in the form of wealth or control. However, it is important to note that sometimes political and economic interests do not align perfectly together. This is evidenced by repeal of the Corn Laws in Britain. The House of Lords had to give the okay to repeal the laws, but most of the members of the House of Lords where landowners who benefitted from the Corn Laws. Interests can explain their decision by emphasizing the political pressure being put on them by groups such as the Anti-Corn Law League which was fighting against the measures. Thus, the House of Lords decided that their political interests in retaining legitimacy without giving up control was more important than the wealth and improved economic situation gained by a continuation of the Corn Laws.