The rules were deemed necessary because “the constraints imposed by market forces might either be too slow and weak or too sudden and disruptive” (Delors Committee, 1989). Economic convergence was expected to follow almost automatically from competitive pressures.
But the fiscal rules were not fully enforced, macroeconomic imbalances mounted and markets behaved as expected: in spite of the no-bail-out clause, for years sovereign risks were underestimated; then they were overestimated. The crisis also made clear the close linkage between sovereign risk and bank risk.