Maplight.org is extraordinary — a database that links US legislators with their votes and the money they received from interest groups.
Consider, for example, H.R.5684 – U. S.-Oman Free Trade Agreement. This is a bill to enact a free trade agreement between the U.S. and Oman. Among the organisations lobbying for the Bill were aircraft manufacturers, pharmaceutical giants, construction companies, oil & gas companies, etc. In short, the usual suspects. Maplight reveals that legislators who voted in favour of the bill received about twice as much in contributions than those who opposed it ($163,111 to $80,856). Conversely, Representatives who voted against the bill received, on average, twice as much from lobbyists opposed to it as those who voted for. Information on campaign contributions comes from the incomparable Open Secrets site.
Money talks. When you look at the list of industries that give most to US legislators, you begin to understand how crazy intellectual property laws get passed.