The study looked at data from OECD countries between 1970 and 2008 to test the Balassa-Samuelson hypothesis. They found that there is no strong support for this hypothesis. Instead, they discovered a consistent negative relationship between productivity in the tradable sector and the real exchange rate. This contradicts the Balassa-Samuelson theory. The results also showed that the impact of other factors on the exchange rate is not very strong, except for the terms of trade.