It's somewhat significant, but not HUGE deal in the big scheme of things, IMHO. The vast majority of people or organizations who invest in Treasury securities are institutional investors who do their own creditworthiness analyses independently of the big three ratings agencies, so the downgrade only really matters to a small portion of investors. In addition, it got down graded ONE NOTCH from AAA to AA+. It's still REALLY GOOD investment-grade material. I mean, I wish my grades were that good At the most, this raises interest rates slightly.