Trichotomy for the orbits of a hypercyclic operator on a Banach space

We obtain a trichotomy for the orbits of a hypercyclic operator $T$ on a separable Banach space $X$: (1) every vector is mean asymptotic to zero; (2) generic vectors are absolutely mean irregular; (3) every hypercyclic vector is mean divergent to infinity. Examples of weighted backward shifts on ${\mathrm{\ell }}^p$ show that all three cases can happen.