There may be other factors than attractiveness involved in why older women have fewer partners. They may be busy putting working in order to put children through college, or just taking care of children may scare the men away, they may find men their age less attractive, or perhaps their sex drive declines, menopause, or their marriage may have put them off men. But being less attractive does sound good as an explanation.
The first thing that we notice from the data is that having children at home seems to only marginally decrease the odds of having two or more partners in the last twelve months. Secondly, compared to the never married, we notice that divorcee's are over twice as likely to be riding the carousel, and more than five times more likely than the cohabiting; divorcee's seem sexually willing.
What we also see is a drop off in the partner count as women get older. Now, it's true that this may be due to female factors independent of attractiveness, and I imagine dating burnout is a factor, but menopause is not an issue, since most women enter menopause in their late 40's and the data suggests that child caring is only a small component of this decline.
But the common lament amongst the femmentariat is that men don't want to commit, or in other words, there are suitable males who want women for sex but not marriage. This implies that women are pursuing men with the "if I give him sex he will marry me" strategy. Therefore, it is not female choosiness that is limiting sexual activity but male choice.
I imagine that there are two factors at play. Firstly, amongst the pool of men that are unmarried, they can be divided into the sexually attractive and unattractive. Secondly, as the sexually unattractive males are "invisible" to women seeking a mate, this means that divorcee's must compete with remaining pool of attractive males. The relative scarcity of attractive men and the surfeit of divorced women mean that it is men who exercise mating choice. The older women are getting less hit upon.
What I find most interesting however is the data listing the odds of having five or more partners by age group. Most of the women who've clocked up five or more notches have done it by their late 20's. Does having so many when they are young destroy some ability to bond. We all know that the children from divorcees have a higher divorce rate, but perhaps promiscuity, too, somehow destroys the commitment capability.