The solid line is the baseline projection - it's what happens if all of the tax cuts magically expire on schedule, there's no alternative minimum tax reform, there's no Medicare drug benefit, and discretionary spending growth is limited to 2.7% per year. The most realistic scenario is, frankly, that the tax cuts are made "permanent," there is AMT tax reform, there is a Medicare benefit, and discretionary spending grows much faster than 2.7% to keep up with population growth and to fund the latest war against whoever we're at war with.