The indicator "mean years of schooling (MYS)" has been one of two education indicators in the Human Development Index calculated by UNDP since 2010. In view of greatly expanded role of education in modern development, this study develops a multivariate panel regression model of socio-economic factors where changing rate of MYS becomes the dependent variable. This research develops a model of socio-economic determining factors where changing the rate of MYS is the dependent variable. The proposed model will include five independent variables to assess the impact on MYS for 97 countries from 1995 to 2017. The most important finding is that dependency with a negative impact on MYS was the most influential factor, followed by urbanization with a positive impact on MYS. The impact from income with a positive impact and population with a negative impact was the third most important factor depending on the income and urbanization subgroup. This study highlighted the offsetting impact of dependency rate and urbanization rate to length of education depending on the income and urbanization subgroups of countries. However, the general policy implications proposed here are subjected to substantial revision if the analysis of scaling results from income and urbanization subgroup analysis are incorporated, because the impact from these two offsetting factors would vary widely depending on the particular subgroup.