The factors that affect Human Development Index have been investigated extensively in previous researches. These studies consider education as an important factor and focus on the quality of education such as teachers' skills, educational facilities and student conditions. Democracy has also been established as an important factor in HDI. In this study, we examined two variables, the democracy index and the land language index as fundamental variables of the Human Development Index (HDI). The land language index is a new variable created to signify the importance of the medium of instruction in higher education institutes, particularly in the Science, Technology, Engineering and Mathematics (STEM) fields. We performed a multiple-correlation analysis with the available data to find the correlation of these two indices on HDI. We found that together, the democracy index and land language index had a strong correlation to HDI. The results of this study can have a significant impact on social scientists and policymakers and should be considered for further research.