Ion densities measured on the dawn-side magnetosheath flank were higher than the dusk-flank. The asymmetry was measured close to the magnetopause, but it became more ambiguous in the central magnetosheath. We show that the asymmetry was at its maximum at the 2009 solar minimum (~ 20 %), but then decreased in the rising stage of the next solar cycle (< 5 %). These results could impact plasma transport processes which are dependent on local magnetopause conditions such as Kelvin Helmholtz Instability.