Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

(N/A) In actinoids,$5f$ orbitals are filled. These $5f$ orbitals have a poorer shielding effect than $4f$ orbitals (in lanthanoids).
Thus,the effective nuclear charge experienced by electrons in valence shells in the case of actinoids is much greater than that experienced by lanthanoids.
Hence,the size contraction in actinoids is greater as compared to that in lanthanoids.