The security of property rights is fragile under dictatorships. This is particularly so if economic agents are uncertain as to whether the regime will last. As a result, private investment is withheld and economic performance is poor. Spain was in such a situation after World War II. However, as the Cold War intensified the United States became interested in Spain as a military ally, thereby helping to consolidate Franco's regime. This led to an increase in economic confidence and helps to explain why economic growth resumed in Spain ahead of significant changes in its autarkic economic policies.

What was the impact of American aid to Spain during the 1950s? This article revisits this question, addressing it from a rather different perspective to the focus on the relief of supply bottlenecks that dominates the existing Spanish economic historiography. It suggests that there is a prima facie case for the aid programme to have had a positive effect on private agents' expectations. The American backing, as part of the process of international acceptance of the Franco regime, may have provided a «commitment technology» that solved problems of credibility, which would have otherwise hindered investment and hence the resumption of economic growth. The paper concludes with an agenda for further research.