Solar wind flow quantities such as matter flux, momentum flux and energy flux, may be closely related to the mechanism responsible for the evolution of the solar wind. In the highly supersonic flow regime their study is facilitated by the fact that the contribution of thermal motions to the momentum and energy fluxes is negligibly small, and thus all three quantities are expressible in terms of proton density n and flow velocity u. If a relation between n, u and heliocentric distance r can be established, the study of these quantities is further simplified. In the following we point out that such a relation does in fact exist, and comment on its implications.