A debt’s maturity profile might be much more important than its amount.
Having said that what I really wanted to comment on is when Wolf writes “It is possible to imagine a ´sudden stop´ on higher risk sovereigns bonds. That would force the debt to become short-term – a classic route to a crisis” and this is clearly another very real risk. In this respect, an insistence by the US Treasury to try to collect on the benefits that a drop in long term rates could have reviving the housing market, by buying back longer term bonds and as a consequence shortening the maturity profile of the US public debt, is exposing the US, and us, to some very dangerous risks.