The purpose of this paper is to show that the cross-section factorization relation σnn(s)/σγp(s) = σγp(s)/σγγ(s) is satisfied experimentally in the energy domain [Formula: see text], where the σ's are total cross-sections and nn denotes the even portion of the pp and [Formula: see text] total cross-section. A convenient phenomenological parametrization for a global simultaneous fit to the pp, [Formula: see text], γp and γγ total cross-section data together with the ρ-value data for pp and [Formula: see text] is provided by using real analytic amplitudes. Within experimental errors, we show that factorization is satisfied when we unfold the published γγ data which had averaged the cross-sections obtained by using the two different PHOJET and PYTHIA Monte Carlo results. Our analysis clearly favors the PHOJET results and suggests that the additive quark model, together with vector meson dominance, allows one to compute σγp(s) and σγγ(s) from σnn(s) with essentially no free parameters. The universal ρ-value predicted by our fit, i.e. ρnn = ργp = ργγ, is compared to the ρ-value obtained by a QCD-inspired analysis of [Formula: see text] and pp data, including the p-air cross-sections from cosmic rays. The ρ-values obtained from the two techniques are essentially indistinguishable in the energy region [Formula: see text], giving us increased confidence in our parametrization of the cross-sections needed for the factorization relation.