Step 1: Understanding the Question:
The question asks for the establishment year of NITI Aayog.
Step 2: Key Concept:
NITI Aayog (National Institution for Transforming India) is the premier policy 'Think Tank' of the Government of India. It was established to replace the 65-year-old Planning Commission.
Step 3: Detailed Explanation:
The Government of India, through a resolution of the Union Cabinet, established NITI Aayog on January 1, 2015.
This move was aimed at fostering cooperative federalism and moving away from the centralized planning approach of the Planning Commission to a more collaborative, 'bottom-up' approach.
Step 4: Final Answer
NITI Aayog was established in 2015.