Economic changes have helped to change the population structure of India.
In 1985, India had a typical population structure of a developing country with large numbers of young children and a rapidly decreasing number of older people. This was caused by:
A high birth rate since having a large number of children was seen as an asset - they could help work on the farm and look after their parents in their old age.
Life expectancy of older people was low due to the lack of good medical care and poor access to clean water.
Although there is a large number of children under 15, this is no longer increasing and there is a sign of a decline in the number of very young children 0-5 years old. This is caused by:
A decline in birth rates. As more people work in secondary and tertiary jobs, children are seen as less of an asset and so the birth rate has dropped.
The development of the economy has improved the education of the population and so more people are pursuing a career before having children, resulting in smaller families.
The life expectancy of older people has increased due to improvements in medical care, particularly in the use of vaccinations and improved sanitation, reducing the number of deaths due to water-borne diseases.