The 1981 article "Average IQ values in various European countries" by Vinko Buj is the only international IQ study that over a short time period has compared IQs using the same IQ test. It was probably done in the 1970s in the capital cities or in the biggest town in 21 European countries and Ghana.[3] Rindermann (2007) disputes the quality of this study, claiming it doesn't provide enough information regarding how it was done.[4]