To interpret the Human Development Index (HDI) of North America, Central America, and the Caribbean accurately, the most important factor to consider would be:
Canada and the U.S. have significantly higher scores than the rest of the countries.
This is because the HDI is an average, and the high scores of Canada and the U.S. can skew the overall average, making it appear higher than it might otherwise be if considering the lower HDI scores of countries in Central America and the Caribbean.