In May 2017, the base year of the All India Index of Industrial Production (IIP) was revised to which of the following years?

Introduction / Context:
This question relates to India's Index of Industrial Production (IIP), a key economic indicator that measures changes in the volume of production in various industrial sectors. Periodically, the base year for such indices is revised to reflect structural changes in the economy and to keep the index relevant. In May 2017, the Government of India announced such a revision for the IIP. Remembering the new base year is important for questions on macroeconomic data and official statistics.

Given Data / Assumptions:
- The question specifically mentions the revision in May 2017.
- Four possible base years are offered: 2011-12, 2015-16, 2016-17 and 2012-13.
- It is assumed that you know India has moved from older base years like 1993-94 and 2004-05 to a more recent one in 2017.

Concept / Approach:
The IIP base year was earlier 2004-05. In May 2017, it was revised to align with newer national accounts and other indices, choosing 2011-12 as the new base year. This revision brought the IIP in line with the base year used for the Gross Domestic Product (GDP) series and other macroeconomic indicators. The other options, such as 2015-16 or 2016-17, were not adopted as the base year in that revision, though they represent later time periods.

Step-by-Step Solution:
Step 1: Recall that prior to 2017, the IIP was based on the 2004-05 series. Step 2: In May 2017, the government updated the base year to reflect more recent industrial structure and to harmonize with the national accounts base year of 2011-12. Step 3: Note that 2015-16 and 2016-17 are not recognized as base years for IIP in official communications about the 2017 revision. Step 4: Therefore, the correct answer is 2011-12, corresponding to option A.

Verification / Alternative check:
To verify, you can mentally review the sequence of base years for many Indian indices: 1993-94 and 2004-05 were commonly used earlier, and then a shift to 2011-12 took place for GDP, Wholesale Price Index and IIP around the mid-2010s. This consistency in selecting 2011-12 as a base year across multiple series supports the choice and rules out other years like 2015-16 or 2016-17.

Why Other Options Are Wrong:
Option B, 2015-16, and option C, 2016-17, are later fiscal years, but they were not chosen as base years in the 2017 IIP revision. Option D, 2012-13, also does not align with the officially adopted base year. The distinction matters because the base year must represent a reasonably stable, recent period and be consistent with other macroeconomic series; 2011-12 was selected for that role.

Common Pitfalls:
Candidates often confuse the IIP base year with base years of other indices or assume that the newest possible year must have been chosen. Another common error is to forget that statistical agencies prefer a year for which complete and consistent data are available, and that they often use the same base year across multiple indicators for comparability. Keeping a small list of updated base years for indices like GDP, IIP and WPI is useful for quick recall in exams.

Final Answer:
In May 2017, the base year of the All India Index of Industrial Production was revised to 2011-12.