Birth rates can be affected by government policies, eg China's One Child Policy (1979-2015).
GNI per capita only shows economic development and says nothing about whether people in a country have a good standard of living. It is an average and may hide differences in wealth within a country.
HDI is widely recognised as a good measure of development since it takes into account more than one indicator and includes economic and social indicators.
Patterns of development
In 1980 the Brandt Report divided the world into the poor south and the rich north. Since that time global patterns of development have become more complex, with countries such as Brazil, India and China developing rapidly.
The HDI index map illustrates the complexities that the Brandt line fails to display.
Classifying levels of development
The World Bank classifies the level of development of a country by using gross national income (GNI) per capita. It classifies countries into:
low-income countries (LICs) - GNI per capita of $1,045 or less
The development continuum is a sliding scale from least to most developed, with lots of intermediates such as the newly-industrialised countries. NICs are countries that have recently seen a massive growth in their manufacturing industries. They include Mexico, India and Malaysia.