This interdependence has pushed up the costs linked to the use of national currencies in a Single Market in terms of conversion costs as well as costs of hedging against risks of appreciation or depreciation. Economic thinking also developed profoundly between the 1970s and the 1990s.
At the beginning of the 1970s, what we called Keynesianism was still very influential among economic policy-makers in the European Community. The "Monetarist counter-revolution" shook it up completely. The Phillips curve and the economic policy trade-offs it appeared to allow were called into question. Above all, it was the stagflation of the 1970s that further indicated the limits of activist policies.