Structure of Benzene

Benzene protons show a chemical shift of 7-8 ppm and that is higher than the chemical shift of H-atoms attached to other sp2-hybridized carbons. Why is that? The explanation invokes a ring current in the pi-clouds of aromatic systems which enhances the external magnetic field outside of the ring and diminishes it inside the ring.


Figure. The MP2(full)/6-31G* optimized structure of benzene.