  Different shares of distinct commodity sectors in production, trade, and
consumption illustrate how resources and capital are allocated and invested.
Economic progress has been claimed to change the share distribution in a
universal manner as exemplified by the Engel's law for the household
expenditure and the shift from primary to manufacturing and service sector in
the three sector model. Searching for large-scale quantitative evidence of such
correlation, we analyze the gross-domestic product (GDP) and international
trade data based on the standard international trade classification (SITC) in
the period 1962 to 2000. Three categories, among ten in the SITC, are found to
have their export shares significantly correlated with the GDP over countries
and time; The machinery category has positive and food and crude materials have
negative correlations. The export shares of commodity categories of a country
are related to its GDP by a power-law with the exponents characterizing the
GDP-elasticity of their export shares. The distance between two countries in
terms of their export portfolios is measured to identify several clusters of
countries sharing similar portfolios in 1962 and 2000. We show that the
countries whose GDP is increased significantly in the period are likely to
transit to the clusters displaying large share of the machinery category.
