  The transverse size of q q-bar fluctuations of the longitudinal photon is
reduced relative to the transverse size of q q-bar fluctuations of the
transverse photon. This implies R(W^2, Q^2) = 0.375 or, equivalently,
F_L(W^2,Q^2)/F_2(W^2,Q^2) = 0.27 for x = Q^2/W^2 << 1 and Q^2 sufficiently
large, while R(W^2, Q^2) = 0.5, if this effect is not taken into account.
Forthcoming experimental data from HERA will allow to test this prediction.
