You are trying to relate measurements of economic activity that are not directly correlated. Gross national product (GNP) is a measurement of the total output of finished products from a country. The critical term is "finished" products - Third World countries may have and export large amounts of raw materials but do not have the resources to manufacture goods from those materials.
Per capita income (PCI) divides the amount of income realized in a country by the population of that country. PCI gives an average figure which may provide a rough means of comparison between countries, but doesn't recognize variables such as income from sources other than sales of goods. Comparing PCI levels also doesn't recognize the differences in the cost of living between countries.
The percentage of a country's population involved in producing finished goods could impact the PCI, depending on wages paid for the labor, and the production of those goods would be reflected in the country's GNP. There are too many variables, however, to draw any reliable relationships between components.