Illustrative comparison between the evolution of energy density for a component with a constant or nonconstant EoS (arbitrary scaling). The blue component has a constant EoS parameter w = −0.8. The green component has a nonconstant EoS parameter w, which starts out with w = −0.8 (equal to the blue component) and evolves in two steps (indicated by the black vertical solid lines) to w = −0.9 (the slope is indicated by the dashed orange line) and finally to w = −1 (the slope is indicated by the dashed red line). The final density at the present time is higher for the green component.