A long theoretical literature has analyzed optimal patent policy design, yet there is very little empirical evidence on a key parameter needed to apply these models in practice: the relationship between patent strength and research investments. I argue that the dearth of empirical evidence on this question reflects two key challenges: the difficulty of measuring specific research investments and the fact that finding variation in patent protection is difficult. I then summarize the findings of two recent studies that have made progress in starting to overcome these empirical challenges by combining new data sets measuring biomedical research investments with novel sources of variation in the effective intellectual property protection provid...