Median number of sexual partners: Feminist X makes a good point that we shouldn't assume that a given number of sexual partners now and in the past measures the same trait. The same guy who had two partners in the past might have 20 partners now.
My earlier analysis only covers the past three decades, so I think the period is short enough to assume that we're measuring the same thing in each of the three decades (80s, 90s, 00s). But it's always better to check.
The mean number of sex partners for white men ages 30 to 39 looks like it hasn't changed much since 1980, but the mean is a poor statistic to use because it is very sensitive to the handful of guys with many, many partners. The median is much better: it was seven partners in the 80s and 90s, and it's six in this decade. Cultural conditions don't seem to have changed much.