GDP/GNP are often used as a global development indiator to show the average income for a country, expressed in $ so that it is easy to read and compare.
gross domestic product: is the value of all goods and services produced by a country in a year
gross national product: is the GDP of a country plus any money that has been earned by investment abroad (ex. earnings from companies working abroad) it is often expressed per capita which means the total figure is divided by the total population
HDI/GDP/GNP can hide social inequalities within a country. for example, Saudi Arabia, with its oil wealth has a high GDP and also a high HDI so ranks well on a global scale. however, wealth is concentrated in the hands of a few people, and for most of the population, living conditions, health care and education are poor = greater social inequalities. it it estimated that the gini coefficient is around 0.459