The Digital Economy Factbook (The Progress And Freedom Foundation)

The Progress and Freedom Foundation is a "is a market-oriented think tank that promotes innovative policies for the digital age" that is heavily supported by various telecom companies and telecom trade associations and may well be carrying the water for them on a variety of issues. Regardless of the organization's funding or basic purpose, it has recently put together a very useful 188 page Digital Economy Factbook (full text download here) filled with charts, graphs and summaries on virtually everything digital including digital media, electronic commerce and threats to the digital economy with all of it exhaustively endnoted.

The attached chart is taken from the section on threats to the digital economy: