My wife just learned that her cousin's husband has Parkinson's. I have a cousin with the disease, as well as a brother-in-law. For a disease that affects less than 0.5% of the population, that strikes me as an unusually high incidence rate for one extended family. I've tried doing some searches on the incidence of the disease, but can only get current data. What I'm curious about is comparative data. Does anyone know of any authoritative studies that show the rate of increase in the incidence of this disease over, say, the past 10 years or so?