Step 1: Identify the topic.
The question is about the Human Development Index, or HDI, and which option is NOT a part of it.
Step 2: What HDI measures.
HDI was created by the United Nations to show overall human well being, not just money. It looks at the quality of life people enjoy.
Step 3: The three real dimensions.
HDI is built from three things: a long and healthy life (life expectancy), knowledge (education levels), and a decent standard of living (per capita income).
Step 4: Match the options.
Per capita income, average life expectancy, and education levels are all official parts of HDI. So they are included.
Step 5: Find the odd one.
Poverty percentage is measured separately by other indexes. It is not one of the three HDI dimensions.
Step 6: Final answer.
The item not related to HDI is poverty percentage.
\[ \boxed{\text{Poverty percentage}} \]