Halogens and the free energy of activation in a resonant benzene system
Resonance between a carbon and a halogen atom decreases as we move down the series $\ce{F, Cl, Br, I}$.  This is because overlap is most effective between orbitals of the same size.  Therefor, carbon-fluorine overlap, both involving $\ce{2p-2p}$ orbitals should be much stronger than carbon $\ce{2p}$ orbital overlap with the $\ce{3p, 4p, etc_{.}}$ orbitals in the larger halogens.  Consequently carbon-halogen resonance becomes less significant as we move down the halogen series.  If we now consider that 1) the resonance and inductive effects for the para-halogens are in opposition to each other (tend to counteract each other) and 2) the resonance effect decreases as we move down the halogen series, then the order of halogens in the Table you mentioned makes sense.