Final answer:
The areas where Senegal and Chad are most similar are not explicitly provided without specific data, but health and life expectancy are possible common areas due to life expectancy trends in different regions with various income levels.
Step-by-step explanation:
Based on the provided information, the areas where Senegal and Chad are most similar can be assessed by looking at various factors that influence the standard of living. These factors include health, education, human rights, crime and safety, and environmental quality. While per capita GDP is often used as an indicator, it cannot fully capture the complexity of what constitutes the quality of life. The data points to the fact that life expectancy can be similar in countries with varying income levels, suggesting that health and life expectancy could be an area where Senegal and Chad might show similarities despite economic differences. Without specific data or a chart directly comparing Senegal and Chad, it is unfeasible to definitively state which area they are most similar in. However, these metrics generally provide the context for comparison and suggest that health and life expectancy could be a common ground.