The economic thoughts of what constitutes the prosperity of the societies have been questioned since ancient philosophers. However, wealth of the nations which was identified with the amount of precious metals by the Mercantilists and identified with the land by Physiocrats, has started being addressed as a phenomenon identified with trade since Adam Smith in parallel with the Industrial Revolution. Within the framework of the traditional international trade approach since the period in question, the high export volume of the countries has begun to be seen as a positive contribution to the growth and development of the countries. On the other hand, the degree of complexity of countries' export structures is seen as the driving force for sustainable growth. In this context, the relationship between the level of economic complexity and the per capita GDP level for the founding countries of OECD is examined for the period 1990-2016 in this study. Findings of the panel cointegration analysis have not revealed a statistically significant long-run relationship for the panel. However, findings indicate in terms of countries that there is positive relationship for Austria, Canada, Greece, Ireland and the US while there is negative relationship for Norway.