Mean spectral index as a function of the YSO evolutionary stages in different star-forming regions (blue triangles: Taurus-Auriga (Dzib et al. 2015); green cross: Perseus (Pech et al. 2016); orange square: Ophiuchus (Dzib et al. 2013); pink dot: Serpens (Ortiz-León et al. 2015); gray dot: IRDCG14.2, separated in G14.2-N (black dot) and G14.2-S (black diamond)). We note that black and gray symbols are SED-based Stage classifications (Povich et al. 2016) and the groups could be different if a different classification scheme was employed. The black dashed line at α = −0.1 draws the boundary between thermal emission and nonthermal emission.