That's a good question. When amendments were made to the act in 1996, I think it was, and in 2005, this issue was discussed a number of times. Frankly, I don't know how this would enhance the principle of transparency. The money paid to a lobbyist doesn't indicate whether the lobbying has had an impact. Is a lobbyist successful because he has been paid more than another one? I don't think so.
On March 23rd, 2011. See this statement in context.