Final answer:
The most common type of interest group is an economic interest group, which includes business, labor, agricultural, and professional groups. Examples include the United States Chamber of Commerce and the Service Employees International Union (SEIU).
Step-by-step explanation:
The most common type of interest group is an economic interest group. Economic interest groups focus on issues such as wages, industry protections, job creation, and profit maximization. They can be further sorted into subcategories such as business, labor, agricultural, and professional. For example, the United States Chamber of Commerce is a business group that advocates for policies that help create jobs and grow the economy. Another example is the Service Employees International Union (SEIU), which represents the interests of workers in healthcare, public services, and property services. In Germany, the German Trade Union Confederation (DGB) acts as an umbrella organization for eight labor groups and represents the interests of close to six million German workers.