Unfortunately the data seems to be limited, and quite poor, at this time. I'm guessing this probably stems both from under reporting due to societal stigmas an

Unfortunately the data seems to be limited, and quite poor, at this time. I'm guessing this probably stems both from under reporting due to societal stigmas and due to a lack of research. However, I found the following meta-analysis that appears to indicate an increase in interest over the past decade and a half. You may be able to access these articles through you're local library for free, or if you have a subscription. I do not have a subscription at this time so I'm unable to retrieve the full details. I previously looked into this topic in 2011 when I was still a psych undergrad, there appears to be more research since then. https://psycnet.apa.org/doiLanding?doi=10.1037%2Fcfp0000074 https://psycnet.apa.org/doiLanding?doi=10.1037%2Fcfp0000074 https://www.tandfonline.com/doi/full/10.1080/0092623X.2016.1178675 https://www.tandfonline.com/doi/full/10.1080/0092623X.2016.1... https://www.sciencedirect.com/science/article/pii/S2352250X22001890 https://www.sciencedirect.com/science/article/pii/S2352250X2... A survey from YouGov in 2016 and again in 2020 appears to indicate non-monogamy is a growing preference among millennials. https://today.yougov.com/society/articles/27639-millennials-monogamy-poly-poll-survey-data https://today.yougov.com/society/articles/27639-millennials-...