A low-quality patent system threatens to slow the pace of technological progress. Concerns about low patent quality are supported by estimates from litigation studies suggesting that most US patents granted should not have been issued. We propose a new model for measuring patent quality, based on equivalent patent applications submitted to multiple offices. Our method allows us to distinguish whether low-quality patents are issued because an office implements a low standard or because it violates its own standard. The results suggest that quality in patent systems is higher than previously thought. Specifically, the percentage of granted patents that are below each office's own standard is under 10% for all offices. The Japanese patent office has a higher percentage of granted patents below its own standard than those from Europe, the USA, Korea, and China. This result arises from the fact that Japan has a higher standard than other offices.