The maximum decadal growth in population of India is registered in the period :

Concept. The change in a population across a census decade can be described in two different ways. The absolute increase is simply the closing population minus the opening population. The decadal growth rate expresses that same increase as a percentage of the opening population: (closing − opening) ÷ opening × 100. The two are not interchangeable — a decade that begins from a much larger base can post a bigger absolute rise while still growing at a lower rate. In Census of India and MoSPI reporting, the "decadal growth" of population is the percentage rate, so periods are ranked on the rate rather than on the raw difference.

Application. Read the "Population (India) (Millions)" column of the table and work each offered period out the same way.

1. Take the opening and the closing population of the period from the table, both in millions.

2. Subtract to get the absolute increase for that decade: increase = closing − opening.

3. Divide the increase by the opening population and multiply by 100 to get the decadal growth rate.

4. Repeat for every offered period, then compare the rates.

The highest rate in that comparison is 24.80%, recorded over 1961 – 1971.

Cross-check. Two independent checks agree. First, 24.80% is the highest decadal growth rate India has recorded in any post-independence census decade, and the rate has fallen in every decade since, down to 17.64% for 2001 – 2011 — the ordering produced above matches that known downward trend. Second, notice what happens if "growth" is misread as the raw absolute increase: the biggest increase is 182.31 million over 1991 – 2001, with 2001 – 2011 less than a million behind it. That different ranking is precisely why the percentage rate, the standard demographic measure of decadal growth, is the basis for comparison here.

Answer. The maximum decadal growth in India’s population, 24.80%, falls in 1961 – 1971.