CPI is difficult and flawed, but they do try to account for size. Soda is pretty consistent in size (12oz can), but, for example, yogurt which can come in a var

CPI is difficult and flawed, but they do try to account for size. Soda is pretty consistent in size (12oz can), but, for example, yogurt which can come in a variety of sizes is added to the CPI per 8oz. The hard part is how you measure the quality change. The market is flooded with high end higher quality yogurts. Yogurt shelves in the grocery store look very different than they did 15 years ago before Chobani kicked off the Greek yogurt crazy, and completely different than 30 years ago before USDA organic certification.