The dipole moment of phenol is smaller than that of methanol. Why?

(N/A) In phenol, the $C-O$ bond is less polar due to the electron-withdrawing $-I$ effect of the $sp^2$ hybridized carbon of the benzene ring, which pulls the electron density away from the oxygen atom.
In methanol, the $C-O$ bond is more polar due to the electron-releasing $+I$ effect of the methyl group, which pushes electron density towards the oxygen atom.
Consequently, the net dipole moment of phenol $(\mu = 1.54 \ D)$ is smaller than that of methanol $(\mu = 1.71 \ D)$.