The Washington Post offers this report, which begins:

Washington’s lobbying industry has mushroomed over the past decade but the government has fallen behind in keeping track of the billions of dollars a year that lobbyists spend, according to a study by the nonpartisan Center for Public Integrity.
Lobbying expenditures in Washington have at least doubled in the past six years, the center reported. Last year, corporations, labor unions and interest groups spent more than $3 billion trying to influence the federal government, up from $1.6 billion in 1998.
At the same time, the center said, enforcement of lobbying regulations has been lax. The center estimated that at least 14,000 disclosure documents required under a 10-year-old lobbying law were not filed over the period, including documents that should have come from 49 of the nation’s 50 largest lobbying firms.

Those interested in money spent on lobbying for civil rights changes might want to check out this page from the Public Integrity’s impressive database.