If you get married, will you get more sex and better sex? So far as I know, a methodologically persuasive study has never been done. That would involve following people over time as they stayed single or got married or got unmarried, and seeing how their sexual behavior and sexual satisfaction changed (or didn’t change) with those transitions. All we have are studies that compare married and single people at one point in time. You can never know from those kinds of studies if any differences really are about being married vs. single or whether they are about any of the many other ways that married and single people differ other than in their marital status. With that qualification, here’s what we know.
The most relevant reviews of the evidence on getting married and (not) getting sex
Chapter 2 of Singled Out
Other articles that may be of interest
I. Sex in and out of marriage
II. Sex and the single person
III. Let’s not be too conventional in our thinking