Why are d Electrons Less Effective in Shielding Nuclear Charge?

[asdf1]

Why are the d electrons less effective in shielding the nuclear charge than the s or p electrons, and are thus more polarizing?

 

[Astronuc]

I believe it has to do with Spherical Harmonics of the wave equation - there is more azimuthal dependence for the d electrons than p or s.

 

[asdf1]

thank you very much!