Another factor is the era of degenerative illness caused by the man. The modernization process is another factor. The evolution of health care and modern medicine such antibiotics, drastically reduced to infant mortality rates and increased the average of life expectancy which together with the decline in fertility rates subsequent reflects a transition to chronic diseases and degenerative diseases as causes of death.
The population growth has been and is very uneven depending on the countries, being much higher in the developing countries than in the developed countries. In developed countries the living conditions that have impacted to reached phase IV are the highly industrialization, population enjoys a high standard of living made possible by the wealth and technology, thus technology today plays a key role in the level of development of a country. Also, the countries that have reached the phase IV are those where women are encouraged to gain a high level of education. Families can afford an additional salary and have better life style. Lastly, in developed countries the majority of its population have access to health care and contraception is almost universal so that there is a control of birth at all levels. In contrast, developing countries have do not have these privileges. The level of poverty is high. Health care is not accessible to the majority of its population and there are high levels of malnutrition.