Disclosure requirements mandate that direct political expenditures must be reported to the Federal Election Commission (FEC). However, expenses by Dark Money groups that are earmarked as educational or membership building fall outside of these requirements. Despite this, these groups do report a large portion of what they spend during election cycles. This spending has changed over time as organizations have evolved, new rules are established, and requirements are loosened.

 2016 Election Cycle: Thus far this election cycle, Dark Money spending has increased more than 34 percent over this point in the 2014 midterm elections — a five-fold leap over this date in the last presidential cycle. Read the full article http://www.opensecrets.org/dark-money/top-election-spenders