Interest groups have become more common in the US due to the many divisions in American society and opportunities for groups to engage with the government system. Major periods of growth for interest groups included the late 1700s during independence movements, the 1830s-1860s during debates over slavery, and the 1900s onward as groups like the NAACP and farmers' unions organized. People join interest groups for social, material, and ideological reasons, and groups engage in activities like providing information to legislators, grassroots organizing, litigation, and lobbying to influence public policy. While money and campaign contributions can influence policy, other strategies may be more effective. Interest groups are regulated through disclosure requirements and tax laws.