The increase in debt-to-GDP ratios in a number of countries since the start of the crisis has mainly been due to slower growth of tax revenue, a rise in expenditures through automatic stabilisers and, in some countries, the cost of support packages from the financial sector, which implied a large primary budget deficit (d > 0).
An undesirable outcome of a decision to lower the policy-relevant interest rate would be to lead to an increase in the long-term ones, especially if it is so in real terms. This would discourage investment and penalise agents holding longer-term risky assets. To avoid such a problem, any policy rate cut has to be justified on the basis of the prevailing monetary policy framework.