Why did the countries which first benefited from access to the New World – Castile and Portugal – decline relative to their followers, especially England and the Netherlands? The dominant narrative is that worse initial institutions at the time of the opening of Atlantic trade explain Iberian divergence. In this paper, we build new quantitative measures which allow for a comparison of institutional quality over time. We consider the number of crown refusals at legislative assemblies, the number and strength of episodes of coin debasement, the number and strength of ad hoc taxes introduced, and real interest spreads for public debt. There is no evidence that the political institutions of Iberia were worse until the English Civil War.