Mr. Conor O'Kelly:

What I mean by that is the debt-to-GDP ratio as traditionally used. The reason that it is used by bond investors in particular is that as one’s debt-to-GDP ratio falls or improves, the assumption is that one’s ability to pay one’s debts and refinance one’s debts is improving simultaneously. That is why it is used as a good indicator. In the case where an element of the GDP growth has no economic value on the other side, therefore, one’s ability to repay and finance one’s debts are no more improved than they were before the number changed then it is less valuable as a tool for investors to use.

Because of the distortion in this case, we have been told by the CSO that it is not necessarily matched by actual economic activity. Therefore, one's ability to repay and refinance is not matched in the way it ordinarily would be in the case of growth in GDP.