According to a new study from the Sunlight Foundation, lobbying revenue hit $1 billion per year by 2012, nearly doubling over the period from 1998 to 2012. In particular, lobbyists with former government experience have reaped the benefit, with contract revenue jumping 422 percent over that same period.

And when it comes to sheer number of lobbyists, from 1998 to 2012, the quantity grew from approximately 3,000 lobbyists to well over 4,000. That number has actually decreased in recent years from a high of over 5,000 in 2008.

Nonetheless, restrictions on lobbying have clearly had little impact on the growth of the industry.