New report highlights:

• There has been a vast increase in the volume of advertising sponsored by outside groups between 2000 and 2016.
• The share of ads sponsored by outside groups between 2000 and 2016 has increased dramatically.
• Whereas 527 organizations dominated advertising in 2004, super PACs now sponsor the most outside group advertising.
• Dark money groups (also known as non-disclosing groups) have been a consistent presence since 2000 and are much more active before the FEC’s 60-day reporting window. The overall volume of ad buys from dark money groups has increased in recent cycles, and even though the share of ads from dark money groups has declined relative to super PACs, their raw ad totals remain high.
• The vast majority of groups are active in a single election cycle.