  We study two concepts of proportionality in the model of approval-based
committee elections. In degressive proportionality small minorities of voters
are favored in comparison with the standard linear proportionality. Regressive
proportionality, on the other hand, requires that larger subdivisions of voters
are privileged. We introduce a new family of rules that broadly generalize
Phragm\'en's Sequential Rule spanning the spectrum between degressive and
regressive proportionality. We analyze and compare the two principles of
proportionality assuming the voters and the candidates can be represented as
points in an Euclidean issue space.
