This statistical analysis of power spectra of the fluctuating Els¿sser variables, ΔZ¿=ΔV¿ΔVA, covers 3408 hours of interplanetary magnetic field and plasma observations made by experiments on the Helios 1 and 2 spacecraft during the years 1975, 1976, and 1980. The averaged spectra of ΔZ- in the range 2¿10-8 km-1<k*<4¿10-7 km-1 (k*=k/2&pgr;, k is the wave number) are found to show little variation with heliocentric distance, solar wind velocity, and solar activity. The resulting averaged power spectrum of ΔZ- obeys a power law with a slope of -5/3. We suggest that it could be thought of a persistent ''background'' spectrum. The averaged spectrum of ΔZ+, however, is flatter that of ΔZ-. The concurrent decrease of the normalized cross-helicity with increasing heliocentric distance (e.g., Roberts et al., 1987a, b) may therefore mainly result from a decrease of ΔZ+ and not from an increase of ΔZ-. This finding places an observational constraint on theoretical models for the evolution of cross-helicity. ¿ American Geophysical Union 1990