The size of the debt itself, in absolute terms, is not very meaningful. It has to be looked at in relation to the size of the economy. That's why in the fiscal sustainability report we look at the debt-to-GDP ratio. A growing debt could be very worrisome if the economy is shrinking, or it could be not that big a deal if the economy is expanding at a fabulously high rate. That's why we look at the debt-to-GDP ratio.
We define “sustainability” as a debt level or debt-to-GDP ratio that is not constantly increasing, because that clearly is unsustainable over the longer term since the debt keeps not only growing but also growing as a share of the national economy.
We've defined “sustainability” as debt in our study, in our report, that at the end of the period is roughly at the same level in relation to GDP as it was at the beginning of the period. That's how we define “debt-to-GDP” or “sustainability”. That's consistent with the practices of other international organizations or institutions that have looked at fiscal sustainability.