This is a standard way of measuring fiscal sustainability. The OECD and the IMF and all the other countries do exactly the same thing.
The measure we use is to take the debt-to-GDP ratio of a jurisdiction, whether it's the provincial or the federal government, for the time being—let's say in 2012.
Sustainability means that, over a long period of time—in this case 75 years—the current policies will allow the government to go back to that debt-to-GDP ratio, the present debt-to-GDP ratio.
For example, in the case of provincial, local governments, we see that if the current policies continue, with the demographic changes, the debt-to-GDP ratio of that sector will significantly increase.
The fiscal gap is what they need to do to bring that debt-to-GDP ratio back to the current level after 75 years; it is 1.9% of GDP. If they reduce their spending or increase their revenues or a combination of the two equal to 1.9% of GDP of today, and maintain that at 1.9% of GDP over the 75-year period, their debt-to-GDP ratio will not increase, it will come back to the current level, which is about 31.5%.