Step 1: Understanding the Question:
According to Census 2011 data on religious composition of India's population.
Step 2: Key Figures:
Hindu \(\approx 79.8\%\), Muslim \(\approx 14.2\%\), Christian \(\approx 2.3\%\), Sikh \(\approx 1.7\%\), Buddhist \(\approx 0.7\%\), Jain \(\approx 0.4\%\).
Step 3: Compare the four given options:
Among Sikh, Jain, Christian and Muslim, Jain has by far the smallest population share.
Step 4: Final Answer:
\[ \boxed{\text{Jain}} \]