The study tested a new method to improve accuracy in estimating price elasticities of substitution for food and beverages in Vietnam. By using instrumental variables, the method reduced bias from measurement errors and unobserved quality changes better than other approaches. The results showed that this new method performed significantly better in correcting for endogeneity bias and controlling for errors, with fewer assumptions needed. However, it still assumes that price changes do not affect quality and requires suitable instruments for accurate estimation.