Initial measurements of the Venus bow shock obtained by Pioneer Venus in 1979 near solar maximum indicated that the bow shock was on average 2.44 RV from the center of the planet in the terminator plane. This is 0.35 RV further from Venus than observed by Venera 9/10 in 1976. In the past this discrepancy has been attributed to some effect of the solar cycle. Recent measurements by Pioneer Venus support this interpretation. In 1980 the distance to the bow shock reached a maximum of 2.45 RV and since then has been almost steadily declining toward toward the distance measured by Venera near solar minimum. The variation in bow shock positiion is well correlated with the sunspot number and the F 10.7 cm flux over this period. We attribute this behavior to the variation in the neutral atmosphere of Venus with the solar cycle and its subsequent effect on the mass-loading of the solar wind.