French poster for the 1979 elections to the European Parliament
In 1973, the same year the UK, Ireland and Denmark joined the Common Market, the first petrol crisis started, multiplying the cost of petrol by four. This made the process of European integration difficult as nations struggled to cope with economic havoc and unemployment.
Enlargement meant that relations between countries of the Common Market needed deepening (i.e. an ever closer union). Hence the setting up in 1974 of the European Council which brought together the Heads of State or of Government several times a year to determine policy (it was not, initially, any more efficient than the Council of Ministers which was handicapped by the rule of unanimous voting on "important issues").
In 1979, elections by direct universal suffrage gave the European Parliament more credibility but it continued to have little more than a consultative role. Subsequent European Parliament elections have suffered from increasing abstention rates, despite the increasing powers of the institution, due to citizens' indifference, incomprehension, or even hostility; Euroscepticism was already on the rise...
Also in 1979, the EMS (European Monetary System) was created to improve cooperation regarding financial matters.