Which of the following census years is known as the 'Year of Great Divide' in…

Concept: A census year is termed the demographic ‘Divide’ point when it marks the turning year between one long-run population-growth regime and the next — before it, the population trend runs one way (stagnant or declining), and from it onward the trend reverses into sustained continuous growth. In India's demographic history, this turning year is used to split the country's growth history into a stagnant/declining pre-divide phase and a steadily rising post-divide phase.

Application to this item:

• 1911–1921 decade (pre-divide): India recorded a negative population growth rate of -0.31% in this decade, driven by recurring famines, epidemics such as the 1918 influenza pandemic, and very limited public-health infrastructure — the population was stagnant or falling.

• From 1921 onward: Death rates began falling steadily as famine relief and public-health measures improved, while birth rates stayed high, so population growth turned positive from this year onward, and every census since has recorded a higher population than the one before. This reversal recorded at the 1921 census is exactly why demographers call it the Year of Great Divide.

Cross-check against the other offered years:

• 1911: This year falls inside the very decade that recorded the negative growth rate — the population trend had not yet turned continuously positive at this point, so it cannot be the turning-point year.

• 1951: This is the first census after Independence, but by this survey the population had already been rising continuously for a good while — the actual reversal from decline to growth had happened considerably earlier, so this year comes too late to be the divide.

• 1991: This year marks the start of economic liberalisation — an economic/policy milestone, not a demographic growth-rate turning point; the population trend had already reversed from decline to sustained increase many decades before this year.

Since the 1921 census marks the point where the preceding decade's population decline gave way to a sustained rise that has continued in every census since, 1921 is confirmed as the Year of Great Divide.