Singles and couples have probably asked themselves, "How much sex should I have per week?" The "magic" number all depends on a variety of factors, including lifestyle, each partner’s health, sex drive, and age. A recirculated study from the Kinsey Institute for research in Sex, Reproduction and Gender suggests age can act as a predictor for average sex frequency, ranging from once a week to once a month.

Unsurprisingly, researchers at the Kinsey Institute found people between 18 and 29 are having the most sex, with an average of 112 sex sessions per year, or twice a week. Meanwhile, 30 to 39 year olds have sex 86 times per year, which equates to 1.6 times per week. Those in the 40 to 49 age group manage to have sex only 69 times per year, about half the total for 18 to 29 year olds.

Evidently, this drop-off coincides with an increase in age as family obligations, day-to-day stresses, and illness become more physically and mentally taxing. A study in June found physical changes that occur as we age, plus how old we feel, both influence the experience of sex.

"The basic storyline that has emerged from these studies is that, as we get older, our odds of developing chronic health conditions increases and this, in turn, negatively impacts the frequency and quality of sexual activity," wrote Dr. Justin Lehmiller, in a Kinsey Institute post.

Marriage also plays a pivotal role in sex frequency: 34 percent of married couples have sex two to three times per week; 45 percent have sex a few times a month; and 13 percent have sex only a few times a year.

So, is your sex life doomed if you’re not average for your age?

Previous research has found married couples and those in committed relationships who have more sex tend to be happier, but this benefit waned after a certain number. The happiness of the survey respondents increased with more frequent sex, but that frequency could be as little as once a week. Those who had sex four or more times a week did not report feeling any happier than those who had it weekly.

Although couples may start to have less sex with age, women report their sex lives actually get better. A 2016 study presented at the Annual Meeting of The North American Menopause Society in Orlando, Fla., found this was linked to women feeling more comfortable in their skin, which led them to develop more confidence to express themselves sexually, and to communicate their needs to their partner. In other words, these women started to focus less on the frequency of sex, and more on the emotional and intimate aspects of sex, or adapting sex acts themselves.

Sex at any age can be beneficial. Whether couples' frequency is average, above average, or below average, age allows partners to focus on the quality rather the quantity of sex. After all, frequent mediocre sex could lead to sexual dissatisfaction in a relationship, while great sex once in awhile could be enough to keep the spark alive.