Which year is regarded as the defining year to mark

Which year is regarded as the defining year to mark the demographic transition from its first to
the second decisive stage?

The year 1921 is regarded as the defining year or the ‘Year of Great Divide’, because prior to
1921, population growth in India was stagnant. India was in the first phase of demographic f transition till 1921, that was characterised by high birth rate and high death rate. After 1921, India’s ’ population growth never declined and showed a consistent upward trend.