That is from the interesting paper "Who Cares About the Lobbying Agenda" by Kimball et al (2011). It was published in Interest Groups and Advocacy (2012). The abstract:
There has been a longstanding concern about inequality in the representation of interests by organized groups and lobbyists in American politics. The lobbying community in Washington is dominated by corporations, trade associations, and professional associations. In Lobbying and Policy Change, Baumgartner and colleagues find that interest group resources are not a very reliable predictor of policy outcomes. This might lead some to conclude that inequality in interest group representation is not a major problem for American democracy. However, Baumgartner and colleagues suggest that inequality in interest group representation presents itself at the agenda-setting stage. They find that the public agenda is quite different from the lobbying agenda. That is, the types of issues that are most important to the public differ from the types of issues that lobbyists bring to the attention of government officials. We examine public opinion data in more detail to determine if there is greater congruence between the public agenda and lobbying agenda for certain publics (e.g., high SES citizens). We find additional evidence that the lobbying agenda does not reflect the policy priorities of the public. However, we find relatively few differences between the policy priorities of low-income and high-income Americans, suggesting that the lobbying agenda fails to represent the concerns of all income groups.