Misreading or misleading on the economy?

Putting it as diplomatically as possible, the Washington Post's Dana Milbank reports that the White House's economic predictions tend to "miss the mark."

"Over three years," Milbank writes, stating the obvious, "the administration has repeatedly and significantly overstated the government's fiscal health and the number of jobs the economy would create."

Why is this so?

There are three possible explanations. One is that, gosh darn it, mistakes have been made and it's tricky to forecast economics anyway. The second is that "structural changes" in the American economy, like the outsourcing of service sector jobs, have changed the dynamics of tax revenue and economic growth to the extent that historical patterns regarding recessional rebounds aren't bankable anymore. The third reason, of course, is that the administration has been cavalier with facts, hoping to tout any improvement in the economy, no matter how fleeting or inconsequential, as a result of its tax cuts.